Effect of Delay Separation and Short Term Storage of Serum on Thyroid Stimulating Hormone (TSH)

Introduction: Thyroid stimulating hormone (TSH) regulates the level of thyroid hormones synthesized in the thyroid gland. Its measurement greatly facilitates the clinical diagnosis as well as management of pituitary-thyroid diseases. The level of analytes in biological sample is affected by pre-analytical, analytical and post-analytical factors. Objective: To fi nd the effect of delay separation and short term storage on serum TSH level. Materials and Methods: A total of 15 blood samples were collected from the patients visited to the immunoassay laboratory, Department of Biochemistry, BPKIHS for thyroid function test. Serum TSH was estimated on the day of sample collection, after 24 hours in delay separated samples and after seven days in short-term stored sample by sandwich ELISA method (Eliscan, India). Results: There were no signifi cant difference in median serum TSH in baseline and delay separated samples (1.43 (0.18-6.52) IU/mL, vs 1.61 (0.25-6.51) IU/mL, p = 0.069) as well as baseline and short term stored samples 1.43 (0.18-6.52) IU/mL vs 1.57 (0.26-5.75), p = 0.925). Conclusion: There is no effect of delay separation and short term storage on the serum TSH level. So, TSH measurement may applicable in large epidemiological studies which require long transportation time to transport samples to the laboratory. Research Article Effect of Delay Separation and Short Term Storage of Serum on Thyroid Stimulating Hormone (TSH) Basanta Gelal*, Subodh Prasad Gupta, Sharad Gautam, Ashwini Kumar Nepal, Binod Kumar Lal Das, Madhab Lamsal and Nirmal Baral Department of Biochemistry, B. P. Koirala Institute Health Sciences, Dharan, Nepal Dates: Received: 11 February, 2017; Accepted: 18 February, 2017; Published: 22 February, 2017 *Corresponding author: Basanta Gelal, Assistant Professor, Department of Biochemistry, B. P. Koirala Institute Health Sciences Dharan, Sunsari, Nepal, Cell: +9779842172396, Tel No: +977-25525555 Ext. 2461 (O), Fax: +977-25-520251, E-mail: https://www.peertechz.com


Introduction
There has been increased progress on immunoassay of the thyroid stimulating hormone, over the past decades, which greatly facilitate clinical diagnosis as well as management of pituitary-thyroid disease [1]. Large-scale epidemiological studies are needed for the screening of diseases of endocrine systems. It requires the measurement of hormones in blood samples from large numbers of subjects, but there are practical diffi culties in collecting and processing samples immediately in the developing country like Nepal. In large scale screening blood sample may be collected at local centers or clinic and sent unfrozen by courier or routine post to central processing and storage laboratories but analysis is not cost-effective on daily basis in most middle size laboratories. Therefore, samples are stored for a period of time [2].
If the result from a specimen is altered by serum-clot contact enough to exceed the variability expected for physiological processes. The serum-clot contact time represented a unique pre-analytical condition that could change the analyte stability independently of any physiologic condition in the patient [2]. Prolonged contact of serum with the clot can cause pre-analytical variation [3]. So, serum or plasma should be separated from physical contact with cells as soon as possible, unless conclusive evidence indicates that longer contact times do not contribute to result inaccuracy. A maximum limit of two hours was also recommended [4].
Each analyte has a different tolerance to a delay in separating serum from clot. Many analytes are stable for much longer than two hours. In hospitals and outpatient clinics, transportation of specimens from a phlebotomy site to a laboratory sometimes takes longer than two hours. Analyte are usually grouped into time blocks in which serum-clot contact cause no changes in analyte concentrations [2].

Objective
To investigate the effect of delay separation and short term storage by measuring the change in concentration of TSH Hormone (TSH). Open J Thyroid Res 1(1): 007-009.
in blood that will be held at ambient condition for up to 24 hours since venipuncture and stored at 4 ºc for 7 days since venipuncture.

Result
The median (IQR) of baseline serum TSH level was not statistically signifi cant different between delay separated (after 24 hours) sample and short term stored (4 ºc for 7 days)

Discussion
This is hospital based quasi experiment to see the effect of delay separation and short term storage on stability of thyroid stimulating hormone. Stability of hormones in a samples are infl uenced by the length of time after collection, storage temperature and the number of freeze-thaw cycles [6]. The rationale of measuring serum TSH level in clinical setting is different from that in epidemiological settings. In clinical settings, measurement used to fi nd out the normal and abnormal values as well as to assess the degree of abnormality but moderate difference with in the reference range are of etiological interest in epidemiological studies [7]. Delays in transportation of blood specimens to the laboratory may cause systematic changes in hormone concentrations and this could obscure association in epidemiological studies [8]. It is not always practical to process blood samples immediately after collection and should be stored for further analysis in large epidemiological as well as in clinical study [9].
In this study, the baseline serum TSH level is not signifi cantly different as compared to delay separated samples and short term stored samples (Table 1) Progesterone concentrations showed no substantial change over the two days period but testosterone concentrations increased by 23% after one or two days delay in processing. FSH and LH concentrations increased on average by 7.0% and 3.8% per day respectively. In contrast to this, SHBG concentrations decreased on average by 5.8% per day over the two days period [11]. Oddie TH et al. (1979), reported that, signifi cant decline in T4, rT3, TSH and T3, concentration with storage interval, the mean observed rates of decline correspond to 5.3%, 3.5%, 0.9%, and 4.3% per year, respectively but TBG concentrations did not appear to change signifi cantly during storage [12].

Conclusion
TSH is resistant to degradation, immunologically stable, and reasonably insensitive to potential problems associated with routine specimen handling when measured by immunoassay technique. So, it is helpful in large epidemiological studies and small size laboratory which require long transportation time and storage.