American Journal of Pharmacy and Pharmacology 2016; 3(4): 40-45

http://www.aascit.org/journal/ajpp

ISSN: 2375-3900

Keywords Blood Collection Tubes,

Serum Separator Tubes (SST),

Gel Tube,

Vitamin A,

Vitamin D

Received: January 24, 2016

Accepted: May 27, 2016

Published: July 19, 2016

Gel Blood Collection Tube Affecting Test Results

Sawsan Mohammed Ali Hadi

Nutrition Research Institute, Baghdad, Iraq

Email address sawsanmo@yahoo.com

Citation Sawsan Mohammed Ali Hadi. Gel Blood Collection Tube Affecting Test Results. American

Journal of Pharmacy and Pharmacology. Vol. 3, No. 4, 2016, pp. 40-45.

Abstract Accurate laboratory testing requires an understanding of the interactions between

collection tubes and blood specimens which can adversely affect the accuracy of

laboratory test results. The blood collection tubes like plain tube (containing no gel) used

for collection of serum for selected chemistry tests, and serum gel tube contains a clot

activator and gel separator used for various laboratory tests. Gel blood collection tube is

influenced by a number of variables, some of which are controlled by the tube

manufacturer, tube material, centrifugation speed and temperature; separator gel may

release materials that interfere with analytical assays. This study is an investigation of

the effect of gel blood collection tubes on vitamin A retinol, 25-OH vitamin D assays by

HPLC method.

1. Introduction

Fig. 1. Gel tube & plain tube (no gel).

American Journal of Pharmacy and Pharmacology 2016; 3(4): 40-45 41

“Serum-separator tubes, also known as SST, gel tubes, are

widely used in the clinical laboratory for routine collection

blood, it contain silica particles as a clot activator and a

special gel (the gel is composed of inert components, which

are part of a polyester-based proprietary formulation) [1]”.

The gel forms a physical barrier between serum and blood

cells during centrifugation, supernatant serum aspirated

directly from the collection tube.

“Gel blood collection tube is influenced by a number of

variables, some of which are controlled by the tube

manufacturer, tube material, centrifugation speed and

temperature; separator gel may release materials that

interfere with analytical assays [2]”.

“Several previous studies from USA, Japan, China,

Canada, and Iraq have shown the effects of interfering of gel

on clinical assay such as: gel may interfere with assays and

affecting analyte concentrations stability of blood analytes

after storage in BD SST tubes for 12 mo, Clinically

significant changes occurred only in 1,25-dihydroxyvitamin

D and retinol-binding protein [3]”.

“Separator gel may add materials, adsorb blood

components, or interact with protein and cellular components

[4]”. “Separator gels lead to a decrease in serum drug

concentrations [5]”. “Separator gels may release materials

(e.g., gel pieces and silicone oil) into the specimens and

spuriously interfere with assays [6]”.

“The separator gel components (SST) were the source of

interference in the quantitation of serum testosterone levels

[7]”. “Blood for 25-OH D measurement is probably best

collected into plain tubes without anticoagulants or gels [8]”.

“Gels have adverse effects on some steroid assays, including

HPLC methods for 25-OH D [9]”. “Unusual chromatography

– especially for 25OHD2 – was noted for some patient

samples. An investigation prompted the hypothesis that gel

separator in the blood collection tubes may cause interference

[10]”.

“It was noteworthy that some unexpected peaks appeared

in blood specimens collected in the particular blood

collection tube [11]”. “Serum 25OHD in VACUETTE tubes

with gel and clot activator, as measured by the Siemens

system, produced significantly higher values than did

samples collected in VACUETTE tubes with no additives

[12]”.

“Laboratories and tube manufacturers should be aware of

the limitation of using any tubes containing gel-separator

[13]”. “Vitamin D3 determination by HPLC cannot be

carried out with all gel tubes [14]”.

“Further studies have showed that an anomalous result

from gel tubes for vitamin D [15]”. “A recent blood

collection problem in our setting Troponin, Vitamin A, and E

[16]”.

“Blood collection tubes that contain separator gel

interfered with the quantification of steroid molecules 17-

hydroxyprogesterone and aldosterone by introducing

extraneous molecules that interfered with LC-MS/MS

analysis [17]”. “The serum TT3 concentrations obtained with

the SST tubes showed a significant positive proportional

difference compared with glass and Vacuette tubes [18]”.

“Do not use serum separator tubes for therapeutic drug

monitoring or toxicological analysis. The plastic serum

separator material extracts lipophilic substances (most

drugs), resulting in a falsely low drug concentration result.

Instead, collect the specimen in a plain red-top tube

containing no anticoagulants or preservatives [19]”.

The aim of the present study is to investigate if gel tubes

cause chromatographic interference with vitamin A (retinol)

and vitamin D (25OHD3) analysis by HPLC method.

2. Methods

Blood samples were collected from three healthy

volunteers into two tube types, gel separator serum tubes, and

plain tubes (tubes with no gel).

Blood collected in a plain tube (no gel), allow blood to clot

at room temperature for 30 minutes then centrifuge for 10

minutes to separate serum from clot.

Gel separator tube: gently invert the tube several times

(eight times). Allow blood to clot at ambient, temperature for

20-30 minutes. Centrifuge for 10 minutes to separate serum

from clot, If frozen serum is required, pour off serum into

plastic screw-cap vial and freeze [20].

Vitamin A assay by HPLC

Assay the concentration of vitamin A, by using HPLC

system knauer with a smart line UV detector 2500, pump

1000, and manager 5000. C18 column [250×4.6 mm (I.d.); 5

µm bead size]. The chromatographic separation was

performed by a mixture of methanol, water (95:5 by volume)

at a flow rate of 2.5 mL/min; Detection was monitored at 287

nm. The quantitative results were expressed as ug/dl vs.

control and calibrator.

Vitamin D assay by HPLC

Assay the concentration of vitamin D, RP- C18 column

(100 x 4.6 mm I.D.; particle size, 5 micron) at a flow-rate of

1 ml/min, the mobile phase was methanol. The eluate was

monitored with photodiode-array detector with wavelengths

265 nm. The quantitative results were expressed as ng/dl vs.

control and calibrator.

3. Results

Patient samples collected in gel separator tubes showed

that;

The chromatogram of retinol and 25OHD were Unusual,

they were not similar in shape, not identical the peaks differ

in height and there was a new peak present in gel tube sample

than the same patient samples collected in plain tubes (no

gel) (Fig. 2 and Fig. 3) and (Fig. 4 and Fig. 5)

The chromatography from the gel separator tubes may

affect the quantitation of both retinol and 25OHD.

42 Sawsan Mohammed Ali Hadi: Gel Blood Collection Tube Affecting Test Results

Fig. 2. Chromatogram of patient, serum collected into plain tube, vitamin A had a retention time of 2.3 minutes and 3.0 minutes for the internal standard,

retinol concentration ug/dl.

Fig. 3. Chromatogram of the same patient, serum collected into (gel tube), retinol Concentration ug/dl.

American Journal of Pharmacy and Pharmacology 2016; 3(4): 40-45 43

A new and unusual peak present between retinol and internal standard and the peaks show differ in height which effect the

concentration and vitamin result.

Comparing the chromatogram of vitamin D in serum collected in plain tubes and those collected in gel tubes, the results

were obtained as in (Fig3 and Fig4).

Fig. 4. Chromatogram of patient, serum collected into plain tube, vitamin D had a retention time of 3.7 minutes and 6.3 minutes for the internal standard,

vitamin D concentration ng/ml.

Fig. 5. Chromatogram of the same patient, serum collected into (gel tube), vitamin D3 Concentration ng/ml.

44 Sawsan Mohammed Ali Hadi: Gel Blood Collection Tube Affecting Test Results

A new and unusual peak present and the peaks show

differ in heights which effect the concentration and vitamin

result.

Tube comparison study for patient serum collected into

plain tube (no gel) and gel blood collection tubes show the

effects of gel which caused chromatographic interference

with retinol and 25OHD and detect the errors which affect

the ability of clinical laboratories to produce accurate

results.

4. Discussion

Ideally, the gel in blood collection tube should be inert to

the specimens collected in.

The gel components in blood collection tube may release

materials (gel pieces and silicone oil) into the specimens and

cause chromatographic interference with vitamin A (retinol)

and vitamin D (25OHD) by the HPLC method compared to

plain blood collection tube (no gel).

“Using gel vials for blood collection might cause disturbed

chromatograms caused by ingredients of the gel. We

recommend using EDTA plasma or serum vials without gel

[21]”. Finally, evaluation of blood collection tubes by reference

clinical laboratories should be done to help in detecting tube-

related errors and interferences in test results which can

adversely influence patient outcomes and decrease laboratory

efficiency.

Table1. shows blood collection tubes-majority of

laboratories collect blood either in plain tubes or gel tubes.

For 25-OH vitamin D analysis;

Many laboratories collect blood specimen in a plain tube

(containing no gel) such as UWHC Lab, Regional Medical

Laboratory, NMS Labs, and Quest Diagnostics.

Other laboratories use gel blood collection tube and plain

tube (no gel) such as Mayo medical laboratories, Labcorp,

and Laboratory Corporation of America.

Other laboratories reject using gel blood collection tube

such as UWHC Lab.

For vitamin A (Retinol) analysis;

Many laboratories collect the blood specimen in a plain

tube (containing no gel) such as MLabs, Clinical Test

Catalog, Department of Pathology, and Lenco Clinical

Reference Laboratory

Other laboratories use gel blood collection tube and plain

tube (no gel) such as Mayo medical laboratories, UWHC

Lab, Labcorp, and Laboratory Corporation of America.

Other laboratories reject using gel blood collection tube

such as NMS Labs, MLabs, Clinical Test Catalog, and

Department of Pathology.

Laboratories should pay attention to the specimen types;

using wrong tube may make the blood sample unusable and

affect the clinical decision. Pre-analytical steps required for

laboratory testing results and any blood collection tubes

should be evaluated and compared the results obtained for

new and current tubes.

Table 1. Blood collection tubes specimen required in medical laboratories.

Medical laboratories Collection Container/Tube

Vitamin A (Retinol)

Collection container/Tube

25-OH vitamin D

Mayo medical laboratories

http://www.mayomedicallaboratories.com/test-catalog/Specimen/60298 A

http://www.mayomedicallaboratories.com/test-catalog/Specimen/83670 D

Preferred: Plain tube

Acceptable: Gel separation tube

Preferred: Gel separation tube

Acceptable: Plain tube

UWHC Lab

http://www.uwhealth.org/lab-test-directory/ A

http://www.uwhealth.org/lab-test-directory/D

Preferred; Plain tube

Acceptable; Gel separation tube

Acceptable; Plain tube

Rejection; SST

Regional Medical Laboratory

http://www.rmlonline.com/site/labtests/3603650?section_id=11 A

http://www.rmlonline.com/site/labtests/3603730 D

Preferred; Gel separation tube Preferred; Plain tube

NMS Labs

http://www.nmslabs.com/uploads/PDF/2010_04_12_DBUpdate.pdf A

http://www.nmslabs.com/tests/Vitamin-D--25-Hydroxy--D2-and-D3---Serum-

Plasma/7628SP D

Rejection; Gel separation tube Preferred; Plain tube

MLabs, Clinical Test Catalog, Department of Pathology

https://www.pathology.med.umich.edu/handbook/#/details/1020

Preferred; Plain tube

Rejection: Gel separation tube

Labcorp, Laboratory Corporation of America

https://www.labcorp.com/wps/portal/provider/testmenu

Preferred; Plain tube or Gel

separation tube

Preferred; Plain tube or Gel

separation tube

Lenco Clinical Reference Laboratory

http://www.lencolab.com/about_us/about_us.html

http://www.lencolab.com/doctors/test%20menue.html

Preferred; Plain tube

Quest Diagnostics

http://www.questdiagnostics.com/home/physicians/testing-services/by-test-

name/vitamin D

Preferred; Plain tube

Specimen Container;

Plain tube, red top tube, (No-Gel)

Gel blood collection tube, gel separation tube, serum gel, SST

American Journal of Pharmacy and Pharmacology 2016; 3(4): 40-45 45

5. Conclusions

Gel collection tubes caused chromatographic interference

with vitamin A (Retinol) and vitamin D (25OHD)

quantitation by the HPLC method compared to serum

collection tubes by plain tube (containing no gel).

Gel blood collection tubes may adversely influence patient

outcomes, patient treatment, patient monitor, patient

diagnosis and decrease laboratory efficiency, and affect the

clinical decision. Standardization of collection tube procedure will be an

important element in accurate analysis.

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