Effect of Temperature on the Stability of Thyroid Stimulating Hormone in Dried Blood Spots

The results showed that the precision of the methods was acceptable and a highly significant correlation existed between them. However, the TDA method has no calibrant between zero and 10·0 flog/ml, thus for trough results and apnoea prevention TDA precision would be improved by a 5 flog/ml calibrant, though the specificity of the immunogen is not stated for this concentration. Simple method programming, standard curve storage, and single point calibration made the Fluorostat easy to use and reduced the cost of single test assays. The dedicated fluorimeter, reagent shelf-life (12-15 months at 4°C), and simple technique ensured assay availability-an advantage over radioimmunoassay and chromatographic methods. The capital outlay for the HPLC and TDA systems are similar, and although the cost per test by TDA is higher, they compare favourably with EMIT3 and are offset by its faster response and shorter laboratory worker time to complete the assay. The TDA Fluorostat, also applicable to other drug assays, therefore provides a practicable solution for assaying theophylline in clinical laboratories.