Effects of long-term storage of filter paper blood samples on neonatal thyroid stimulating hormone, thyroxin and 17-alpha-hydroxyprogesterone measurements

Abstract

Objectives Clinical laboratories store filter paper samples used in neonatal screening for various periods of time after performing hormonal measurements. However, due to lack of data concerning specimen stability, it is unclear for how long these samples should be stored. The objective of this study is to determine the stability and reproducibility of thyroid-stimulating hormone (TSH), thyroxine (T 4 ) and 17-hydroxyprogesterone (17-OHP) measurements in filter paper blood samples stored for up to 60 months. Methods Two hundred and twenty-eight blood samples, drawn between the second and the fourth day of life, were divided into seven distinct groups and kept at 4-88C for one day or 2, 12, 24, 36, 48 or 60 months after basal hormonal measurements. In each group, TSH, T 4 and 17-OHP levels were initially assayed 24-48 hours after collection (basal) and repeated once at the end of storage timing. All the measurements were performed by time-resolved fluorometry (1235 AutoDELFIA, Wallac Oy, Turku, Finland). Repeated and basal levels of each hormone were compared within the same group by Student's paired t-test. Differences were considered significant at P , 0.05. Results Compared with basal measurements, TSH and T 4 levels declined significantly only when these hormones were re-assayed at 48 or 60 months of sample storage. In contrast, 17-OHP concentrations decreased earlier, starting at 24 months and continuing throughout the remaining period. Conclusion Our data suggest that neonatal screening of filter paper samples kept at 4 -88C are reliable for repeating the hormonal measurements when specimens are stored for up to one year, in the case of 17-OHP, or three years, in the case of T 4 and TSH.

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

“…The stability of TSH in this study (30 days at RT and up to 60 days in the refrigerator or freezer) was shorter than the 36 months reported by Lando and cols. (6) for samples collected from newborns on filter paper and stored in a refrigerator (2-8 o C), and also shorter than the 2.7, 4.1 and 6.5 years for samples stored at RT, 4 o C and -20 o C, respectively, reported by El Ezzi and cols. (7).…”

“…Although the pertinent literature is quite limited (2)(3)(4)(5)(6)(7)(8), it is undeniably important to establish the best drying and storage conditions of blood samples collected on filter paper for newborn screening. The samples are frequently exposed to different climate conditions during drying and transport to the laboratories, a fact that may influence the test results.…”

“…This interpretation is supported by Adam and cols., (8) who found that TSH and T 4 degradation on filter paper is three and ten times greater, respectively, in samples stored at higher humidity. In addition, other factors such as the quality of the filter paper used, the way the blood was placed on filter paper, the time of blood elution, and even the method of hormone determination may interfere with TSH results and stability (6).…”

“…Despite the simplicity of this method, which does not require venipuncture and simplifies sample transportation from distant regions to a central laboratory, questions arise about the possible interference of sample drying, storage and transportation under different physical conditions and of the quality of filter paper with the stability of the hormones (2)(3)(4)(5)(6)(7)(8).…”

Long‐term stability of thyroid hormones and DNA in blood spots kept under varying storage conditions

“…This was later confirmed by Elvers et al 7 . A recent report 8 showed that screening of filter papers is reliable for TSH and TT4 after storage of specimens for three years. However, this study tested the stability of filter spots only at 4°C–8°C.…”