Effects of drying and storage conditions on the stability of TSH in blood spots

Abstract

Objective: To evaluate the influence of sample drying and storage temperature on TSH stability in neonatal screening. Subjects and methods: Blood samples from 29 adult volunteers as a surrogate for neonatal blood (10 with normal TSH, 9 with overt hypothyroid and 10 with subclinical hypothyroidism) were spotted on filter paper and dried at 22°C or 35°C for 3 hours. The samples were then stored at 22°C, -4°C, or -20°C, and TSH measurements were performed at day 0 (D0), D7, D30, D60, D180, and D360 of storage. Results: The drying temperature did not interfere with TSH measurement on D0. TSH values remained stable up to D30 when stored at 22°C and were stable up to D60 when stored in a refrigerator or freezer. Samples stored at 22°C had a greater decrease in TSH values than samples stored in a refrigerator or a freezer. Conclusions: Freezer storage is not advantageous compared to storage in the refrigerator. At the end of one year, if confirmation of the initial result is required, a reduction of TSH concentrations should be taken into account. Arch Endocrinol Metab. 2018;62(2):201-4

How Long are Residual Newborn Screening Specimens Useful for Retesting when Stored in Suboptimal and Uncontrolled Conditions of Temperature and Humidity?

“…When evaluating TSH stability, and similarly to those described for several authors, our results showed a poor stability resulting from a fast degradation rate, strongly influenced by the adverse humidity conditions. In quantitative terms, the estimated TSH recovery obtained from our logarithmic trend curve at 1 year of storage was similar (47.3 %) to those reported by Magalhães et al (47.7 %) [13].…”

“…Nine studies evaluated 3 or more storage temperature conditions, but all included at least one condition corresponding to room or ambient temperature. Four investigations conducted part of their evaluations in environments of high humidity [5,9,11,14], one stated desiccants were not used (8), three did not describe their humidity conditions being supposed that they were ambient humidity [12,[16][17], and the remaining five worked in controlled conditions [6,7,10,13,15]. These diverse scenarios highlight the difficulties faced when an objective comparison is attempted between the results of previously published experiences and the results of this paper.…”

“…Magalhães et al [13] analyzed DBS from 29 adults with different TSH levels, stored at -20 °C, 4 °C and 22 °C along a 1-year period of storage wrapped in aluminum foil envelopes. TSH values remained stable up to 30 days when stored at 22 °C and was stable up to 60 days when stored in refrigerator or freezer.…”

“…In summary, six of the previously discussed investigations evaluated the stability of different markers in the short-term (1 month) (5,(9)(10)(11)(12)14), five in the medium-term (1 to 2 years) [6,8,13,15,17], and two in the long-term (12 and 15 years) [7,16]. Three investigations conducted their studies using newborn DBS specimens [6,7,16] but in all cases samples corresponded to healthy or screen-negative newborns.…”

An exploratory study of short-term camping in Antarctica: Hormonal and mood states changes

“…For measuring thyroid hormone concentrations, drops of blood were collected on a filter paper (Whatman S&S 903 Screening Cards, Life Sciences, GE Healthcare, US), dried horizontally, stored in plastic bags with silica, and kept away from exposure to light and hot temperatures. Dried blood spot disks (each 3.2 mm in diameter) were plated, diluted in europium buffer solution, and analyzed by time-resolved two-site fluoroimmunoassay with direct double-sandwich technique (AutoDELFIA Neonatal hTSH and Auto DELFIA Neonatal T4; WallacOy, Fin-land), as previously reported in a similar study (Manousou et al 2020, Moraes et al 2020, Magalhães et al 2018. TSH sensitivity is typically better than 2 µU/mL, and T4 sensitivity is typically better than 1.5 µg/dL.…”