Erwin SchleicherClinical Chemistry/Central Laboratory

University Clinic Tübingen

(Thessaloniki, 16. – 19. May 2019)

Discrepances of blood glucose and HbA1c in diabetic patients – How to proceed in individual cases

Joint International Scientific Meeting „Diabetes Mellitus“ From basic research to the day to day clinical practice

Diagnosis of Diabetes mellitus

(cut-off values)

Clinic Laboratory

1a. HbA1c ≥ 6,5%or

1. Plasma glucose (fasting)≥ 126 mg/dl (7 mmol/l)

or2. oGTT (75g Gluc) 2h-value

≥ 200 mg/dl (11 mmol/l)or

3. Random plasma glucose≥ 200 mg/dl (11 mmol/l)

important to monitor metabolic control to prevent complications

(ADA 2009)

Is Glucose an old horse in the

Diagnosis of Diabetes mellitus??

Case 1

Diagnosis of Diabetes mellitus by HbA1c

After one year she moved to another city. Visting another doctor

she was told not having diabetes but rather being healthy.

WHY?

Case from the Internet:A 27 year old female American reported that an HbA1c of 7,6 % was found during an „Health check-up“. The young lady, now with the diagnosis Diabetes was treated with daily insulin injections.

After extensive anamesis of the doctor the lady mentioned that her spleen was

removed after an accident HbA1c-value is elevated

no insulin patient healthy!!!!

Basic question:

Is the HbA1c value technically/analytically wrong?

e.g. interference factors

or

The value is right, but the interpretation is wrong?

e.g. because of glycemia-independant influence factors

Definition of HbA1c and formation of HbA1c(indirect glucose measurement!)

- stable adduct of D-glucose at the N-Terminus of the ß-chain of HbA0 - is proportional to the glucose concentration and erythrocyte life span

labile stable

Serum proteins are glycated accordingly Fructosamine

Patient S. B. (f) 52 y.

(since 1995 patient of ambulance, University Clinic Jena)

DiagnosisDiabetes mellitus Typ 1 since 1984, treated with insulin, no complicationsDermatitis herpetiformisGliadin-autoantibodies positive since 2003

Control visit 08/2012: No change of diabetes therapy; no change in life styleGluten-free diet

Current therapyActrapid HM (Normalinsulin U 100) 9-9-6-0 IE s.c.Protaphane HM (NPH-Insulin U 100) 5-0-0-8 IE s.c.Simvastatin 40mg 0-0-0-1Valsartan 160 mg 1-0-0-0Amlodipin 5mg 1-0-0-0

Case 2

Dapson 50 mg 1-0-1-0

Explanation: Dapson leads to mild hemolysis reduced erythrocyte life span, which may not always be evident by overt anemiaHere: ~ 10% less Hb, Hct, RBC count on 12/2014

Case 2

HbA1c ~ 6.5% over years,visit 12/2012: HbA1c = 3.8% - but unchanged therapy

in all cases BG is below 8.4 mmol/l = 151 mg/dl

Drugs that can cause hemolytic anemia include:

Cephalosporins, most common causeDapsoneLevodopaLevofloxacinMethyldopaNitrofurantoinNonsteroidal anti-inflammatory drugs (NSAIDs)Penicillin and its derivatives Phenazopyridine (pyridium)Quinidine

Garbe et al. Br J Haematol. 2011;154:644

Case 2

admittance 3 months 6 monthsReference

rangeHbA1c DCA (Siemens) (Ambulance)

9.0 6.6 6.3 4.3-5.5 %

HPLC (Tosoh) (Central laboratory)

6.0 4.9 4.9 4.3-6.1 %

Fasting plasma glucose(mg/dl)

245 126 100 63-100 mg/dl

Case 3

Male diabetic patient (73y) type 1 Diabetes* since 6 years send to the clinic for improvement of metabolic control(*secondary to recurrent necrotizing pancreatitis)

U. Friess, E. Schleicher et al. Clin Chem

Which HbA1c value is right?

© Universität Tübingen

Question to the Auditorium:

How would you proceed?

A) forget about the HPLC value and accept DCA-value

since it fits better to blood glucoseB) send blood to another Lab for HbA1c analysisC) discuss the problem with the LabD) analyse patient‘s blood with the Fructosamine assay

Case 3

Normal (N)

Patient (V)

ß-chain 66 K N

U. Friess, E. Schleicher et al. Clin Chem

Immunological method

Val HisLeu Thr Pro Glu

N-Terminus

Val HisLeu Thr Pro

HbA0

HbA1c

Immunologic method:

antibody glycated hexapeptide

Reference method !!!

Glu

GluGlu

Hemoglobin anomalies

© Universität Tübingen

Which HbA1c method is right/better ?

Immunological less subject to interference (Ab first 6 amino acids)but

HPLC-method may recognizes a “Hb-problem”

An Hb-pathology/mutation may not only interfere with analysisbut may lead to a change in erythrocyte life span

HbA1c value leads to wrong interpretation!

other possibilities, apart from BG Fructosamine

Biological variationsOne suit fits all?

What is “normal“? Reference range?

Influence factors on HbA1c:age: yes (~ 0.1%/10y) gender: ? Hb level? gene: yes (african am.) pregnancy?

Only 50% of the HbA1c variation is determined by the glucose level in healthy peopleRohlfing CL Diabetes Care 2002

Others?

Shortend erythrocyte life span in patients with bad metabolic control ?

Virtue et al.: Diabetes Care 2004

HbA1c in uremic, diabetic patients (in comparison to glycated albumin)

M. Inaba et al.: (JASN 2007)

Glycated albumin is a better glycemic indicator than glycated hemoglobin in hemodialysis patients with diabetes: Effects of anemia and erythropoetin injection

Dm + HD

HbA1c underestimates glycemiaHbA1c of 7.0% 247 mg/dl glucose

Dm - HD

Erythropoetin injections elevate hemoglobin but decrease HbA1c

Fig. 1: Approximately one-third of diabetic dialysis patients have an average HbA1c<6%, referred

to as “Burnt-Out Diabetes”

HbA1c in diabetic dialysis patients

CM Rhee et al. Updates on the Management of Diabetes in Dialysis PatientsSemin Dial. 27: 135–145 (2014)

Dr. Ostendorf (Medical Laboratory Frechen):

Above a reticulocyte count of 32‰ elevated HbA1c values are

decreased.

red: 6,5 % HbA1c Dmgreen: 5,7 % HbA1c NDm

© Universität Tübingen

How can we detect reduced erythrocyte life span?

No method availablebut reticulocyte count indicates de novo synthesis

biological influence be careful when interpreting

- Age up to 0.1% HbA1c / decade

- gender: no difference pregnancy ???- Alcohol consumption ( ) smoke ( )

- forms of anemia incl. Fe-deficit + treatment reticulocyte count- Renal insufficience (hemodialysis) ???- Bad metabolic control

- Genes: ca. 0,4% HbA1c in Afroamericans

- Severe liver disease

Influence factors on HbA1c

Comparison of Glucose and HbA1c Glucose HbA1c

• Interference factors (analyt.) --- hemoglobin variants• Influence factors working muscle ---• fasten/postprandial ---• Influence of rapid change instable in blood sample ---• Biological variation (d to d) 12-15% < 2%• --- erythrocyte-turnover• (Anemia etc.) --- elevated or reduced• Pregnancy --- variable (not recommended)

• Uremia --- variable• Age --- significant increase• Diagnosis very good very good• Metabolic control very good (T1 D.m.) very good (T2 D.m.)• hypoglycemic indicator very good (acute) useless• Prognosic value (vascular) oGTT CHD microvascular lesions

Symptoms of Diabetes (weight loss, polyuria, polydipsia,..)Elevated Diabetes Risk (Diabetes-Risk-Test)

elevated Glukose- / HbA1c values

oGTT75 g oral Glucose tolerance test,≥8-12 h fastened, venous plasma

t=0 min, NPG Fasting plasma glucose

t=120 min, 2 hours plasma glucose

<100 mg/dl<5,6

mmol/l

100-125 mg/dl5,6-6,9 mmol/l

≥126 mg/dl≥7,0 mmol/l

<140 mg/dl<7.8

mmol/l

140-199 mg/dl7,8-11,0 mmol/l

≥200 mg/dl≥11,1 mmol/l

+ IFG oder

No IGT Diabetes Diabetes (Prediabetes)

Fasting plasma glucose or random plasma gluose

(IFG impaired fasting tolerance und IGT impaired glucose tolerance)

HbA1cTake care of patient specific influence factors

<5,7% <39 mmol/mol

5,7 - <6,5%39 - <48 mmol/mol

≥6,5%≥48 mmol/mol

No Diabetes Diabetes

≥126 mg/dl ≥ 7,0 mmol/l

≥ 200 mg/dl≥ 11,1 mmol/lDiabetes

oGTT

Diabetes

Normal results + symptoms or risk/borderline results further diagnosts via oGTT or HbA1c

DDG-guidelines 2018

Diagnosis of Diabetes mellitus

(cut-off values)

Clinic Laboratory

1. Plasma glucose (fasting)≥ 126 mg/dl (7 mmol/l)

or2. oGTT (75g Gluc) 2h-value

≥ 200 mg/dl (11 mmol/l)or

3. HbA1c ≥ 6,5%or

4. Random plasma glucose≥ 200 mg/dl (11 mmol/l)

important to monitor metabolic control to prevent complications

(ADA 2018)

How to proceed if HbA1c and blood glucose values are discrepant:

Analytical variability: - compare with a different method/ask the laboratory

Biological variability: - ~ 50% hereditary i.e. independent of glucose- age, ethnic back ground etc.- important influence factor: erythrocyte life span (CKD, cirhosis) anemia (incl. treatment), Hb-variants etc. other drugs

check hematological parameters incl. Reticulocytes

and/or fructosamine

HbA1c „useless“ in pregnancy and diabetic patients on hemodialysis

Take home message

and

Glucose is not an old horse!

Hans-Ulrich HäringAndreas Fritsche, Norbert Stefan

Rainer Lehmann, Andreas PeterIngo Rettig, Erwin Schleicher