Source: Annals of clinical biochemistry; Jan 2017 ; p. 4563216688924
Publication Date: Jan 2017
Publication Type(s): Journal Article
Abstract:Background TSH is used as the first line test of thyroid function. Siemens Healthcare Diagnostics recommend that Siemens Centaur reagents must be protected from light in the assay information and on reagent packaging. We have compared the effect of light exposure on results using Siemens TSH-3Ultra and FSH reagents. The TSH reagent includes fluoroscein thiocyanate (FITC) whereas the FSH reagent does not. Methods Three levels of quality controls were analysed using SiemensTSH-3Ultra and FSH reagent packs that had been kept protected from light or exposed to light at 6 hour intervals for 48 hours and then at 96 hours. Results TSH results were significantly lower after exposure of TSH-3Ultra reagent packs to light. Results were >15% lower at all three levels of QC following 18 hours of light exposure and continued to decrease until 96 hours. There was no significant difference in FSH results whether reagents had been exposed to or protected from light. Conclusions TSH results but not FSH results are lowered after exposure of reagent packs to light. Laboratories must ensure that TSH-3Ultra reagents are not exposed to light and analyse quality control samples on every reagent pack to check that there has not been light exposure prior to delivery. The labelling on TSH-3Ultra reagent packs should reflect the significant effect of light exposure compared to the FSH reagent. We propose that the effect of light exposure on binding of FITC to the solid phase antibody is causing the falsely low results.