Are Procedures Codes in Claims Data a Reliable Indicator of Intraoperative Splenic Injury Compared to Clinical Registry Data?

Accepted Manuscript

Are Procedures Codes in Claims Data a Reliable Indicator of Intraoperative SplenicInjury Compared to Clinical Registry Data?

Anne M. Stey, MD, MSc Clifford Y. Ko, MD, MS, MSHS, FACS Bruce Lee Hall,MD PhD, MBA, FACS Rachel Louie, MS Elise H. Lawson, MD, MSHS Melinda M.Gibbons, MD, MSHS, FACS David S. Zingmond, MD, PhD Marcia M. Russell, MD,FACS

PII: S1072-7515(14)00322-6

DOI: 10.1016/j.jamcollsurg.2014.02.029

Reference: ACS 7367

To appear in: Journal of the American College of Surgeons

Received Date: 10 November 2013

Revised Date: 24 February 2014

Accepted Date: 25 February 2014

Please cite this article as: Stey AM, Ko CY, Lee Hall B, Louie R, Lawson EH, Gibbons MM, ZingmondDS, Russell MM, Are Procedures Codes in Claims Data a Reliable Indicator of Intraoperative SplenicInjury Compared to Clinical Registry Data?, Journal of the American College of Surgeons (2014), doi:10.1016/j.jamcollsurg.2014.02.029.

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http://dx.doi.org/10.1016/j.jamcollsurg.2014.02.029

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ACCEPTED MANUSCRIPT 1

Are Procedures Codes in Claims Data a Reliable Indicator of Intraoperative Splenic Injury

Compared to Clinical Registry Data?

Anne M Stey, MD, MSc (a, b), Clifford Y Ko, MD, MS, MSHS, FACS (b, c, d), Bruce Lee Hall,

MD PhD, MBA, FACS (c, e), Rachel Louie, MS (b), Elise H Lawson MD, MSHS (b), Melinda

M Gibbons. MD, MSHS, FACS (b), David S Zingmond MD, PhD (b), Marcia M Russell MD,

FACS (b, d)

(a) Icahn School of Medicine at Mount Sinai Medical Center, NY, NY;

(b) David Geffen School of Medicine, University of California Los Angeles, Los Angeles, CA;

(c) American College of Surgeons, Chicago, IL;

(d) VA Greater Los Angeles Healthcare System, Los Angeles, CA;

(e) Washington University in St Louis, Department of Surgery, Olin Business School, and Center

for Health Policy; St Louis VA Medical Center; BJC Healthcare St Louis.

Disclosure Information: Nothing to disclose.

Presented at the American College of Surgeons 99th Annual Clinical Congress, Washington, DC,

October 2013.

Support: Dr Stey’s time was supported for this publication by The Robert Wood Johnson

Foundation Clinical Scholars program and the U.S. Department of Veterans Affairs.

Correspondence address: Anne M. Stey 10940 Wilshire Blvd, Suite 710 Los Angeles, CA 90024. Phone: 310-794-2507

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Fax: 310-794-3288 Email: [email protected]

Running Head: Procedure Codes Capture Iatrogenic Injury

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ABSTRACT

Background: Identifying iatrogenic injuries using existing data sources is important for

improved transparency regarding the occurrence of intraoperative events. There is evidence that

procedure codes are reliably recorded in claims data. The objective of this study was to assess

whether concurrent splenic procedure codes in patients undergoing colectomy procedures are

reliably coded in claims data as compared to clinical registry data.

Study Design: Patients who underwent colectomy procedures in the absence of neoplastic

diagnosis codes were identified from American College of Surgeons National Surgical Quality

Improvement Program (ACS-NSQIP) data linked with Medicare inpatient claims data file (2005-

2008). A kappa statistic was used to assess coding concordance between ACS-NSQIP and

Medicare inpatient claims, with ACS-NSQIP as the reference standard.

Results: A total of 11,367 colectomy patients were identified from 212 hospitals. There were

114 patients (1%) who had a concurrent splenic procedure code recorded in either ACS-NSQIP

or Medicare inpatient claims. There were 7 patients who had a splenic injury diagnosis code

recorded in either data source. Agreement of splenic procedure codes between the data sources

was substantial (kappa statistic 0.72, 95% CI 0.64- 0.79). Medicare inpatient claims identified

81% of the splenic procedure codes recorded in ACS-NSQIP, and 99% of the patients without a

splenic procedure code.

Conclusions: It is feasible to use Medicare claims data to identify splenic injuries occurring

during colectomy procedures as claims data have moderate sensitivity and excellent specificity

for capturing concurrent splenic procedure codes compared to ACS-NSQIP.

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INTRODUCTION

The spleen is injured in 0.4-1% of colectomies, affecting a total of 6,000 patients

annually in the United States.(1,2) Such iatrogenic injuries account for approximately 20% of all

splenic procedures performed.(3-6) Patients subsequently have a 5% lifetime risk of

overwhelming post-splenectomy infection with an associated 38-70% mortality rate.(4,7)Despite

these clinical implications, providers and payers have not focused on intraoperative splenic

injury as a target for quality improvement. Yet, how tissue is handled and intraoperative injury to

surrounding organs, such as the spleen, may be viewed as an indicator of poor technical

quality.(8)

Iatrogenic splenic injury may be an identifiable adverse occurrence in administrative

claims data because injury is often treated with an additional procedure to repair or remove the

spleen. Administrative claims data have been used to measure quality for colectomy procedures

by identifying surgical complications based on the presence of diagnosis codes. However, this

use of diagnosis codes for capturing surgical complications in claims data is limited by

variability in coding.(9-13) Additionally, pay-for-performance programs that impose financial

losses on providers based on the presence of surgical complication diagnosis codes may

encourage under-coding of these diagnoses, effectively decreasing transparency within the health

system.(14-16) There is a need for more valid and reliable data elements than the current

diagnosis codes if claims data are to be used for surgical quality measurement.

One such data element that has shown promise in claims data is the procedure code.

Previous studies using claims data have demonstrated that procedure codes may be more reliably

coded than diagnosis codes. (17-19) Some of these authors have postulated that this difference in

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the reliability of coding may be due to the higher reimbursement potential associated with

procedures.

The overarching goal of this study was to analyze the reliability of using procedure codes

recorded in Medicare inpatient claims data to identify intraoperative adverse events. We

hypothesized that concurrent splenic procedure codes recorded in Medicare inpatient claims data

for patients undergoing colectomy reliably reflect the concurrent splenic procedures recorded in

the American College of Surgeons National Surgical Quality Improvement Program (ACS-

NSQIP). If procedure codes are as reliable for capturing intraoperative events as hypothesized,

these codes could be a means of improving transparency surrounding intraoperative events. This

increased transparency would allow for the health care system to measure and therefore focus on

reducing the rates of iatrogenic intraoperative adverse events, such as splenic injury.

METHODS

Data Source and Measures

The American College of Surgeons’ National Surgical Quality Improvement Program

(ACS-NSQIP) is a surgical clinical registry that collects high quality clinical data with dedicated

trained clinical abstractors in participating hospitals. The Medicare inpatient claims data file is an

administrative dataset comprised of demographic data, as well as diagnoses and procedures

billed to Medicare for all Medicare beneficiaries. Patient records accrued from the ACS-NSQIP

clinical registry from 2005 to 2008 were linked to the Medicare inpatient claims data file from

the same period using indirect patient identifiers and a deterministic linkage algorithm. The

details of the linkage procedure are provided elsewhere.(20) As a result of the linked data source,

the study sample was restricted to patients 65 years of age and older who underwent a colectomy

at an ACS-NSQIP participating hospital from 2005 to 2008. Colectomy procedures were

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identified by Current Procedures Terminology (CPT) codes recorded in the ACS-NSQIP “CPT

primary procedure” data field (Appendix 1, online only). The exclusion criterion was the

presence of colon cancer diagnoses (due to possibility that the cancer could have invaded the

spleen and therefore splenectomy may have been indicated) in any of the ten Medicare inpatient

claims International Classification of Diseases, 9th edition (ICD-9) diagnosis data fields.

Additionally, colectomies in the setting of trauma admissions were not included in this dataset

because ACS-NSQIP does not accrue any patients who undergo operations as a result of blunt or

penetrating trauma.

The primary occurrence queried was the presence of a concurrent splenic procedure

code. This was determined in ACS-NSQIP based on the presence of designated CPT codes in

any of ACS-NSQIP’s ten “concurrent procedure” or ten “other procedure” data fields. This was

determined in Medicare inpatient claims based on the presence of designated ICD-9 procedure

codes in any of the six Medicare inpatient claims “procedure” data fields. CPT and ICD-9 codes

used to identify splenic procedures are reported in Table 1.

The secondary occurrence queried was the presence of a diagnosis code of splenic injury.

This was determined based on the presence of ICD-9 diagnosis codes denoting splenic injury in

the one “postoperative diagnosis” data field in ACS-NSQIP (Appendix 2, online only). In

Medicare inpatient claims, this was determined based on the presence of the same ICD-9

diagnosis codes in any of the ten “ICD-9 diagnosis” Medicare inpatient claims data fields.

Statistical Analysis

Initial descriptive statistics were performed to compare the demographic and clinical

characteristics of patients who underwent colectomy with concurrent splenic procedure (in ACS-

NSQIP and Medicare inpatient claims) to those who did not. The raw rates of ACS-NSQIP

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postoperative complications, including 30-day composite morbidity and 30-day mortality were

calculated to understand the clinical implication of concurrent splenic procedures on

postoperative outcomes. Thirty-day composite morbidity was defined as a dichotomous variable

representing the occurrence of any one or more of the following 30-day postoperative

complications: surgical site infection (superficial, deep and/or organ-space), wound disruption,

sepsis, pneumonia, unplanned reintubation, prolonged intubation, bleeding requiring transfusion,

cardiac arrest, myocardial infarction, deep vein thrombosis, pulmonary embolus, coma, stroke,

peripheral nerve injury, renal failure and urinary tract infection.

Next the clinical implication of a splenic injury requiring a splenic procedure was

quantified. This was done by calculating the association between odds of 30-day morbidity and

30-day mortality and a concurrent splenic procedure while controlling for clinical variables. This

association was calculated using a hierarchical multivariate logistic model including, the hospital

as a random intercept, and the following independent variables selected using clinical relevance

and significance on bivariate analysis, p<0.05; splenic procedure, American Society of

Anesthesiologists Classification, functional status, emergent case status, prior surgery,

preoperative open wound, ascites, impaired sensorium, preoperative pneumonia, dyspnea,

ventilator dependence, chronic obstructive pulmonary disease, congestive heart failure,

preoperative renal failure, steroid use, preoperative transfusion, preoperative sepsis, bleeding

disorder and the CPT linear risk variable. The CPT linear risk variable is the linearly scaled

probability of morbidity (or mortality depending on the model) associated with each CPT code

calculated in a previous hierarchical logistic model controlling for age, American Society of

Anesthesiologists Classification and functional status.(21) This is the current standard method of

adjusting for case-mix in ACS-NSQIP semiannual report models.

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Subsequently, clinical variables associated with the odds of a splenic procedure were

identified using another hierarchical multivariate logistic model. Initial bivariate analysis was

used to select clinical variables most significantly associated, p<0.05, with splenic procedure for

inclusion in the multivariate model. Emergent case, previous surgery and ascites were included

in the model due to their potential clinical importance. The predictive ability of the model was

determined with the C-statistic.

Finally, the concordance between ACS-NSQIP and Medicare inpatient claims procedure

codes was compared. ACS-NSQIP was treated as the gold-standard as it has been shown to have

a high degree of accuracy when compared to other means of perioperative event capture.(22-26)

Percent agreement was calculated by the ratio of patients who were concordant in both ACS-

NSQIP and Medicare inpatient claims over the total number of patients. In order to calculate the

sensitivity, specificity, positive and negative predictive value of Medicare inpatient claims, the

ACS-NSQIP dataset was designated as the reference standard as has been done in previous

studies.(22,24,25) A Kappa statistic and respective 95% confidence interval was calculated to

assess agreement between the data sources beyond chance. Diagnosis codes recorded in ACS-

NSQIP and Medicare inpatient claims were compared in a similar fashion.

A final sensitivity analysis was performed excluding patients with primary splenic

disorders (Appendix 3, online only). This work was approved by the RAND Corporation

Institutional Review Board. All data management and analyses were performed with SAS

version 9.3 Cary, North Carolina, USA.

RESULTS

A total of 11,367 colectomy procedures were identified from 212 hospitals. A total of 114

(1%) patients underwent a concurrent splenic procedure according to either ACS-NSQIP or

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Medicare inpatient claims. Of those 114 patients, 108 patients (95%) underwent splenectomy and

10 patients (9%) underwent splenorrhaphy. A total of 106 (1.2%) patients undergoing open

colectomy had a splenic procedure compared to 8 (0.3%) patients undergoing laparoscopic

colectomy, p<0.001. There was no difference between the two groups for age or gender (Table

2). Notable statistically significant and clinically relevant differences between patients

undergoing concurrent splenic procedure and those who did not were the proportion of cases that

were emergency (non-trauma) procedures (43% versus 27%, p=0.001), as well as rates of

preoperative ascites (10% versus 4%, p<0.001), and preoperative systemic inflammatory

response or sepsis (38% versus 22% (p<0.001).

The postoperative 30-day outcomes were compared between patients who underwent

concurrent splenic procedure and those who did not while controlling for clinical variables and

case-mix (Table 3). Patients who underwent concurrent splenic procedure had 1.8-fold higher

odds of 30-day morbidity (95% CI 1.1-2.8, p<0.01) when controlling for preoperative

comorbidities and colectomy case-mix. This was likely partly attributable to higher rates of

bleeding requiring intraoperative/postoperative transfusion; 11% versus 1%, p<0.0001. There

was no significant difference in 30-day mortality when controlling for comorbidities and

colectomy case-mix.

A hierarchical multivariate logistic model demonstrated that two clinical variables were

highly associated with the odds of a splenic procedure. The variable most highly associated was

the colectomy procedure CPT code, odds ratio = 5.54, 95% CI = 2.87-10.70 and having had a

preoperative blood transfusion in the 48 hours prior to colectomy, odds ratio= 2.22, 95% CI =

1.04-4.75 (Table 4). C statistic was 0.71.

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Procedure codes captured a rate of splenic events within the incidence range reported in

the literature. Concurrent splenic procedures were reflected in 0.7% of colectomies in ACS-

NSQIP and 0.9% in Medicare inpatient claims (Table 5). Using procedure codes, 64 splenic

injuries were captured in both Medicare inpatient claims and ACS-NSQIP using procedure

codes. A total of 35 splenic injuries were captured in Medicare inpatient claims but not ACS-

NSQIP. Another 15 splenic injuries were captured in ACS-NSQIP but not Medicare inpatient

claims. Percent agreement was 99%. Statistical concordance between the data sources on

recording of splenic procedure codes was substantial (kappa statistic 0.72, 95% CI 0.64-0.79).

Medicare inpatient claims correctly identified 81% of the splenic procedure codes recorded in

ACS-NSQIP, and 99% of the patients without a splenic procedure code. Only 1% of patients

without a splenic procedure code in Medicare claims were false negatives.

Diagnosis codes captured a rate of splenic events below the incidence range reported in

the literature. Seven splenic injuries were captured in Medicare inpatient claims using diagnosis

codes (0.06%). No splenic injuries were captured in ACS-NSQIP and therefore the Kappa

statistic could not be calculated. Of note, 57% or four out of seven patients with a diagnosis code

of splenic injury in Medicare inpatient claims were captured by procedure codes in Medicare

inpatient claims. Conversely, 48% or three out of seven patients with a diagnosis code of splenic

injury in Medicare inpatient claims were captured by procedure code in ACS-NSQIP.

A final sensitivity analysis was performed, excluding patients with diagnoses of primary

splenic disorders (Appendix 3, online only). A total of 35 out of 11,367 patients had portal

hypertension, immune thrombocytopenic purpura, splenomegaly or leukemia/lymphoma. Of the

114 patients who underwent a splenic procedure, 4 of them had one of the above diagnoses. The

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analyses were re-run with this sample excluding patients with primary splenic diagnoses and all

findings of these analyses were unchanged from those of the larger sample.

DISCUSSION

Using a linked clinical registry and administrative claims database, this study found the

concordance of procedure codes between claims data and a clinical registry was substantial with

a Kappa statistic of 0.72. The sensitivity of concurrent splenic procedure codes in Medicare

inpatient claims for capturing a splenic procedure recorded in ACS-NSQIP was high (0.81),

while the specificity was excellent (0.99). Furthermore, concurrent splenic procedure codes

representing splenic injury were coded in greater frequency than diagnosis codes representing

splenic injury. Finally, concurrent splenic procedures during colectomy were associated with

worse postoperative 30-day morbidity while controlling for comorbidities and colectomy case-

mix. In summary, this study found that there is substantial concordance in procedure codes

between clinical registry and administrative claims data.

Previous work has shown that administrative data unreliably code diagnoses of surgical

complications in certain circumstances.(9,10,13) Other groups have also demonstrated that

procedure codes may be more reliably coded in administrative data than diagnosis codes.(18,19)

As such, procedure codes in administrative claims data may be useful for assessing occurrence of

adverse events during colectomy compared to using diagnosis codes.

This study’s rates of concurrent splenic procedures during colectomy were within the

range of known incidence of splenic injury for both ACS-NSQIP and Medicare inpatient claims.

(1,2) Of note, Medicare inpatient claims data did have slightly higher rates of capture for

concurrent splenic procedures than ACS-NSQIP, but at the same time the false positive rate in

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Medicare inpatient claims procedure codes is uncertain. The higher capture rate might in part be

due to the more ambiguous nature of ICD-9 codes, which are less granular than CPT codes.

There are also differences in the training of the personnel collecting data as well as the primary

aims in data collection which may add bias to what is captured in the data.

Diagnosis codes in both ACS-NSQIP and Medicare inpatient claims were much lower

than the known incidence of splenic injury. The diagnoses were coded so infrequently that they

are likely inaccurate as they do not represent known incidence of this complication.(27) Previous

studies have demonstrated that diagnosis coding of postoperative complications may be

unreliable and inaccurate in claims data.(22) In addition, ACS-NSQIP limits ICD-9 codes to one

postoperative diagnosis field, which may underestimate apparent diagnosis rates in registry data.

There has been concern regarding the accuracy of diagnosis codes dating back to the era

of establishment of diagnosis related groups. (17) An advantage of procedure codes in

administrative data is that they may be more reliable in capturing health care related events than

diagnosis codes. Some groups have begun to use procedure codes to define the occurrence of

complications.(28) Intraoperative concurrent splenic procedure codes in claims data may be

useful for identifying intraoperative iatrogenic injuries. Since claims data are available for all

patients, this means providers and payers could work together to improve the transparency of

intraoperative events, which could potentiate subsequent quality improvement activities. For

example, if certain providers are identified as having a large number of iatrogenic injuries,

departments could step in and provide coaching or other support. In this way, claims data could

be used for identifying and monitoring surgical quality within an institution.

Indeed, the major source of iatrogenic splenic injury during colectomy is vigorous tissue

handling near the spleen.(4) As such, the resection of left sided colonic tumors has higher rates

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of iatrogenic splenic injury likely due to mobilization of the splenic flexure.(1) Similarly, any

operation requiring mobilization of the splenic flexure, such as subtotal colectomy may have a

higher rate of splenic injury.(29) Yet, simply because an injury is more likely in this anatomic

location, does not make the injury less significant for the patient. Attention should be focused on

what can be done to prevent splenic injury. Giving feedback to providers has minimized other

perioperative complications.(30-32) This study demonstrates a mechanism for detecting splenic

injury with the ultimate goal of using this data to provide feedback to providers and improve

patient care.

The current study has several limitations. First, ACS-NSQIP during 2005-2008 captured

only one data field for postoperative diagnosis codes. Occasionally, the postoperative diagnosis,

regardless of intraoperative events or findings, is inaccurately recorded as “the same as the

preoperative diagnosis”. As a result, the diagnoses of iatrogenic splenic injuries may be under-

captured. Second, using procedure codes may under-estimate the occurrence of iatrogenic

splenic injury to only those injuries requiring a procedure. However, evidence has demonstrated

that 47% of splenic injuries require a procedure.(33) This is concordant with the findings of this

study; that a splenic procedure was performed in around half of patients with a diagnosis of

splenic injury. It has been recommended that splenic lacerations greater than 1 cm, or multiple

lacerations should be treated with splenectomy or splenorraphy.(4) These more severe injuries

are likely better indicators of poor quality. Therefore the exclusion of smaller injuries controlled

with topical hemostatic may be of little importance to quality measurement. A third limitation is

that the concordance of the CPT and ICD-9 procedure codes is limited by the crosswalk validity.

Since this study used two different types of codes: CPT codes captured ACS-NSQIP concurrent

procedures and ICD-9 codes captured Medicare concurrent procedures, the concordance between

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capture in the two datasets was limited by the fact that the descriptions of ICD-9 codes were less

granular than CPT codes. Therefore matching the codes to generate a crosswalk required some

inference on the part of the researcher. A fully concordant crosswalk may not be possible based

on the differences between the CPT and ICD-9 coding systems and their respective definitions.

A fourth limitation is that no provider characteristics were available to identify and adjust for

differences across providers in rates of splenic injuries. A fifth limitation is that colectomies for

cancer were excluded from this analysis. This was done in order to limit the capture of indicated

splenectomies that would have been necessary for adequate surgical resection. However,

indicated splenectomies even in cancer are very rare, and colon cancer is the most common

indication for colectomy. As such, the generalizability of study findings to the wider population

of colectomy patients may have been limited by this exclusion. Finally, it is possible that ACS-

NSQIP abstractors might collect concurrent procedures variably, as they are not perceived to be

as critical as the index procedure code. Although the rate of splenic procedures were within the

published ranges, it is possible that concurrent procedures were under-captured. Furthermore, the

clinically trained abstractors at ACS-NSQIP may also be more discerning, coding only clinically

relevant procedures as compared to administrative claims coders who may err on the side of

capturing all concurrent procedures. Although, it is beyond scope of this study to assess why

Medicare captured more concurrent procedures than ACS-NSQIP, in this era of large datasets,

this question requires a more extensive study to analyze exactly how diagnosis and procedure

codes are recorded. Standardizing data collection techniques are likely just as important as

standardizing how we care for patients if scientists and policy makers wish to use these data for

quality measurement.

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Despite these limitations, the current study adds to the literature by validating the

reliability of procedure codes in administrative claims data for detection of intraoperative events.

Future directions include determining whether procedure codes are useful as a component of

hospital level comparisons. Another important step would be to determine scalability of this

approach, by identifying whether the procedure codes for other iatrogenic injuries during

colectomy can be reliably captured.

CONCLUSION

Procedure codes recorded in claims data for concurrent splenic procedures during

colectomy are more valid and reliable for diagnosing intraoperative splenic injury than diagnosis

codes in claims data. Therefore, in absence of clinical registry data, procedure codes in claims

data may be a means of identifying intraoperative events. Although these intraoperative events

and associated procedure codes are disease-specific, limiting their generalizability, procedure

codes could be extrapolated as an indicator of surgical technical quality. The next steps in this

work include evaluation of other procedure codes that may represent intraoperative

complications, as well as a determination of whether these procedure codes can be used to

evaluate hospital level performance.

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33. Langevin JM, Rothenberger DA, Goldberg SM. Accidental splenic injury during surgical

treatment of the colon and rectum. Surg Gynecol Obstet 1984;159:139-144.

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Table 1. Procedure Code Crosswalk

Description CPT Procedure Code ICD-9 Procedure Code Total splenectomy 38100, 38120 41.5 Partial splenectomy 38101 41.4, 41.42, 41.43 Other splenectomy 38102 41.9, 41.93, 41.99 Splenorrhaphy 38115, 38129 41.95

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Table 2. ACS-NSQIP Characteristics of Medicare Patients Undergoing Colectomy Procedures

with and without a Concurrent Splenic Procedure from 2005-2008 at an ACS-NSQIP

Partipcating Hospital

Preoperative clinical characteristics

Colectomy with

concurrent splenic

procedure

Colectomy without

concurrent splenic

procedure

Total p Value

n=114 n=11,253 n=11,367 n (%) n (%)

Male 56 (49) 4832 (43) 4888 (43) 0.19 Age, y 65-75 75-84 ≥85

51 (45) 48 (42) 15 (13)

5469 (49) 4524 (40) 1260 (11)

5520 (49) 4572 (40) 1275 (11)

0.66

American Society of Anesthesiologists Class 1 or 2 3 4 or 5

27 (24) 49 (43) 38(33)

3533 (31) 5722 (51)

1998 (18)

3568 (31) 5771 (51) 2028 (18)

<0.001

Functional status Independent Partially dependent functional status Fully dependent functional status

69 (61) 19 (16) 26 (23)

9095 (81) 1348(12) 810 (7)

9164 (81) 1367 (12) 836 (7)

<0.001

Approach Open procedure 106 (93) 8835 (79) 8941 (79)

<0.001 Laparoscopic procedure 8 (7) 2418 (21) 2426 (21)

Acuity of illness: Emergency procedure 47 (41) 2995 (27) 3042 (27) 0.001 Previous Surgery within 30 Days 11 (10) 447 (4) 458 (4) 0.002 Preoperative Open Wound 13 (12) 469 (4) 482 (4) <0.001 Recent weight loss >10% 11 (10) 600 (5) 611 (5) 0.04 Body Mass Index >30 28 (25) 2866 (25) 2894 (25) 0.71 Ascites 12 (11) 400 (4) 412 (4) <0.001 Impaired Sensorium 11 (10) 393 (4) 404 (4) <0.001

Pulmonary comorbidities:

Smoker 17 (15) 1349 (12) 1366 (12) 0.34 Chronic obstructive pulmonary disease 21 (18) 1264 (11) 1285 (11) 0.02 Dyspnea 35 (31) 1933 (17) 1968 (17) 0.001 Pneumonia 6 (5) 179 (2) 185 (2) 0.002 Ventilator Dependent 17 (4) 416 (15) 433 (4) <0.001

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Cardiac comorbidities:

History of myocardial infarction 6 4 (4) 176 (2) 180 (2) 0.10 Congestive heart failure 9 (8) 341(3) 350 (3) 0.003 Recent percutaneous coronary intervention 7 (6) 1069 (10) 1076 (10) 0.22 History of cardiac surgery 15 (13) 1271 (11) 1286 (11) 0.53

Renal comorbidities:

Renal failure 7 (6) 240 (2) 247 (2) 0.004 Dialysis 3 (2) 129 (1) 132(1) 0.14

Hematologic and immunologic comorbidities

Bleeding disorder 28 (25) 1127 (11) 1255 (11) <0.001 Blood transfusion 9 (8) 226 (2) 235 (2) <0.001 Systemic inflammatory response syndrome, sepsis, or septic shock

44 (39) 2435 (22) 2479 (22) <0.001

Steroid use 15 (13) 811 (7) 826 (7) <0.001 All clinical variables were derived from ACS-NSQIP. Concurrent splenic procedure definition

included in Table 1.

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Table 3: Association between Occurrence of a Concurrent Splenic Procedure and 30-day Postoperative Morbidity and Mortality for Patients Undergoing Colectomy Procedures

Outcomes

Colectomy with concurrent splenic

procedure

(n=114)

Colectomy without concurrent splenic

procedure

(n=11,253)

30-d postoperative morbidity, n (%) 67 (59) 3794 (34) 30-d postoperative mortality, n (%) 23 (20) 969 (9) Risk-adjusted odds ratio for 30-d postoperative morbidity (95% CI)

1.8 (1.2-2.8)* Reference Group

Risk-adjusted odds ratio for 30-d postoperative mortality (95% CI)

1.1 (0.6-2.0)* Reference Group

*Odds ratio and 95% confidence interval were generated from a hierarchical multivariate logistic

model including, the hospital as a random intercept, and the following independent variables;

splenic procedure, American Society of Anesthesiologists Classification, functional status,

emergent case status, prior surgery, preoperative open wound, ascites, impaired sensorium,

preoperative pneumonia, dyspnea, ventilator dependence, chronic obstructive pulmonary disease,

congestive heart failure, preoperative renal failure, steroid use, preoperative transfusion,

preoperative sepsis, bleeding disorder and CPT linear risk variable. CI= Confidence interval. 30-

day morbidity and mortality variables derived from ACS-NSQIP data. See text for list of

complications included in 30-day morbidity definition. Concurrent splenic procedure defined in

Table 1.

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Table 4. Clinical Variables Associated with the Occurrence of a Concurrent Splenic Procedure

Clinical variables Odds Ratio 95% Lower CI 95% Upper CI p Value*

CPT linear risk 5.54 2.87 10.70 <.0001 Emergency case 0.85 0.54 1.33 0.47 Previous surgery 1.12 0.55 2.26 0.75 Functional status

0.05 Independent -- -- -- Partially dependent 1.23 0.71 2.14 Fully dependent 1.95 1.09 3.50

Bleeding disorder 1.61 1.00 2.60 0.05 Preoperative transfusion 2.22 1.04 4.75 0.04 Preoperative dyspnea 0.65 0.42 1.00 0.05 Preoperative ascites 1.62 0.82 3.17 0.16 *p Value, odds ratio and 95% confidence interval were generated from a hierarchical

multivariate logistic model including, the hospital as a random intercept, and the following

independent variables; emergent case status, prior surgery, functional status, bleeding disorder,

preoperative transfusion, ascites, dyspnea, and CPT linear risk variable. C statistic=0.71.

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Table 5. Identification of Splenic Injury Occurring during Colectomy Procedures using ACS-NSQIP and Medicare Inpatient Claims

for 11,367 Patients

Type of code used to identify

splenic injury in Medicare inpatient

claims

No. of patients captured with

splenic injury in ACS-NSQIP and

Medicare inpatient claims (sensitivity*)

No. of patients captured without splenic injury in ACS-NSQIP and

Medicare inpatient claims (specificity*)

No. of splenic injuries not captured in

ACS-NSQIP but captured in Medicare

inpatient claims

No. of splenic injuries

captured in ACS-NSQIP

but not captured in Medicare inpatient

claims

Agreement beyond chance of

capturing splenic injury between

ACS-NSQIP and Medicare inpatient

claims Kappa (95% CI)

Procedure codes

64/79 (0.81) 11,253/11,288 (0.99) 35 15 0.72 (0.64-0.79)

Diagnosis codes

0/0 (NA) 11,360/11,367 (NA) 7 0 NA

*Using ACS-NSQIP as the gold standard. NA signifies not applicable because too few observations were captured to calculate an estimate.

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Precis

It is feasible to use Medicare claims data to identify splenic injuries occurring during colectomy

procedures as claims data have moderate sensitivity and excellent specificity for recording of

concurrent splenic procedure codes compared to ACS-NSQIP.

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Appendix 1. Current Procedure Terminology (CPT) Codes and Descriptions

CPT Code Case Description

44140 Partial removal of colon 44141 Partial colectomy with ostomy 44143 Partial colectomy with end ostomy 44144 Partial colectomy with mucous fistula 44155 Colectomy with proctectomy 44156 Colectomy with kock pouch 44157 Colectomy with ileoanal anastomosis 44158 Colectomy with pouch anastomosis 44160 Partial colectomy with ileocolostomy 44204 Laparoscopic partial colectomy 44205 Laparoscopic partial colectomy with ileocolostomy 44206 Laparoscopic hartmanns with end colostomy 44207 Laparoscopic colectomy/coloproctostomy 44208 Total colectomy with coloproctostomy 44210 Total colectomy without proctectomy 44211 Total colectomy with proctectomy jpouch 44212 Total colectomy with proctectomy ileostomy 44213 Colectomy take down splenic flexure

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Appendix 2. ICD-9 Diagnosis Codes of Splenic Injury

Description ICD-9 Diagnosis Splenic injury unspecified 865.00 Splenic Injury Hematoma without Rupture 865.01 Splenic injury capsular tear 865.02 Splenic Injury Laceration Extending into the Parenchyma 865.03 Splenic injury complete parenchymal disruption 865.04 Splenic injury open 865.10 Splenic injury open hematoma 865.11 Splenic injury open tear 865.12 Splenic injury open parenchymal disruption 865.14

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Appendix 3. ICD-9 Diagnosis Codes of Primary Splenic Diagnosis

Primary splenic disorder ICD-9 Diagnosis

Portal hypertension 572.3 Immune thrombocytopenic purpura 287.31

Splenomegaly

289.4 289.51 289.52 289.53 789.2

Leukemia/Lymphoma

200.07 200.17 200.27 200.37 200.47 200.57 200.67 200.77 200.87 201.07 201.17 201.27 201.47 201.57 201.67 201.77 201.97 202.07 202.17 202.27 202.37 202.47 202.57 202.67 202.77 202.87 202.97 205.0 205.1 205.2 205.3 205.8 205.9

Documents

Are Procedures Codes in Claims Data a Reliable Indicator of Intraoperative Splenic Injury Compared to Clinical Registry Data?