Effect of Serum Clot Contact Time on the Stability of Thyroid Hormones in Evacuated Collection System

1. Effect of Serum Clot Contact Time
on the Stability of
Thyroid Hormones in
Evacuated Collection System
Dr. Diganta Dey
Ashok Laboratory Clinical Testing Centre Pvt. Ltd.,
Kolkata
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Ashok Laboratory Clinical Testing Centre
Pvt. Ltd.

2. Stability of Thyroid Hormones in
Vacutainer
Clot contact time has
variable effects on the
stability of laboratory
investigations. Present
study was conducted
to check the maximum
retention time of TSH
and T4 stored in clot
vacutainer and in
aliquot of separated
serum .
Clot vacutainer
[Mfg: Beckton Dickinson
and Company (BD),
USA/Greiner Bioone
International ]
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Ashok Laboratory Clinical Testing Centre
Pvt. Ltd.

3. Methodology
• Each specimen collected in triplicates,
taking prior consent from patients, and
control results obtained by analyzing TSH
and T4 from a single tube within 30 min of
collection in Cobas e411 machine.
• Serum was separated from another
vacutainer and last one kept intact.
• The clot vials and serum aliquots preserved
at 4 °C and tested for TSH and T4 on 4th and
again on 7th day from the collection date.
• The results obtained by the testing of
multiple specimens (TSH = 37, T4 = 45)
were compared to their corresponding
control serum, and the variation between
the results from specimens stored in clot
vials and serum aliquots, respectively were
noted.
Roche Cobas e411
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Ashok Laboratory Clinical Testing Centre
Pvt. Ltd.
Assay method:
Electrochemiluminesence
Immunoassay

4. Stability of Analytes up to 7 days of
Retention: Statistical Analysis
DAY 4 DAY 7
Tube Serum aliquot Tube Serum aliquot
TSH #p 0.975 0.962 0.968 0.977
*r 0.999 0.999 0.999 0.999
T4 p 0.501 0.363 0.197 0.103
r 0.990 0.989 0.985 0.989
#p value > 0.05 indicated the difference is statistically insignificant as compared to
sample turned at 30mins taken as control.
*r is correlation coefficient (0.5 ≤ r ≤ 1 indicated good correlation) as compared to
sample turned at 30mins taken as control.
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Ashok Laboratory Clinical Testing Centre
Pvt. Ltd.

5. Results at a Glance : Comparison between TSH Values
Ashok Laboratory Clinical Testing Centre
Pvt. Ltd.
5
0.001
0.01
0.1
1
10
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37
TSH
(
µIU/ml)
No. of sample
TSH (serum in clot contact)
1st day (Control)
4th day (Tube)
7th day (Tube)
0.001
0.01
0.1
1
10
100
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37
TSH
(µIU/ml)
No. of sample
TSH (serum in aliquot)
1st day (Control)
4th day (Aliquot)
7th day (Aliquot)

6. Results at a Glance : Comparison between T4 Values
Ashok Laboratory Clinical Testing Centre
Pvt. Ltd.
6
0
2
4
6
8
10
12
14
16
18
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45
T4
(µg/dl)
No. of sample
T4 (serum in clot contact)
1st day (Control)
4th day (Tube)
7th day (Tube)
0
2
4
6
8
10
12
14
16
18
20
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45
T4
(µg/dl)
No. of sample
T4 (serum in aliquot)
1st day (Control)
4th day (Aliquot)
7th day (Aliquot)

7. Analysis of Test Data
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Ashok Laboratory Clinical Testing Centre
Pvt. Ltd.
TSH and T4 levels were found to be unaltered
(p > 0.05) up to 7 days when the samples
were stored at 4 °C.
The maximum clot contact time (7 days)
showed no interference on the results of the
tested parameters.
No significant difference (p > 0.05) in test
results was observed between the specimens
in clot vials and serum aliquots.

8. Conclusion
This study may be useful to define acceptable
delay time and storage condition when it is
not possible to maintain a short time
between the sample collection and testing.
It will be helpful for the physicians to request
additional testing for thyroid parameters
from the previously retained specimen in the
laboratory.
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Ashok Laboratory Clinical Testing Centre
Pvt. Ltd.