Low-ultraviolet "white" fluorescent lamps fail to protect pyridoxal phosphate from photolysis.

Ag. 1. Evaluation of TSH assays based on redefining assay sensitivity as the " lower limit of interassay quantitative measurement " As iMustrated, e.g., the AbbottEtA for TSH has a lower limit of inter-assay quantitative measurement' of0.3-0.4 miflknt unit&anda lowerlimitofnormal of 0.6 milli-int.unit& and thus by our ciltenais a " sensitivi " assay 1. Determination of the " in-house interassay precision profile curve " (9). Five serum pools with TSH concentrations corresponding to the subnormal (at least two pools) and normal range are included in eight to 10 consecutive routine assays to assess the precision actually achieved by a laboratory over the normal and subnormal range. 2. Graphical assessment of the " in-house lower limit of interassay quantitative measurement " or " lower limit of the assay working range " under routine conditions: this is determined from the intercept of the interassay CV (y-axis) equal to 10% or 15% with the " in-house interassay precision profile " curve. 3. Determination of the " in-house reference range " for euthyroid individuals. 4. Assay classification: an assay can justifiably be called " sensitive " and do-serves further clinical trials in hyper-thyroid patients if and only if the " lower limit of quantitative measurement " falls clearly below the normal range. Or, in other words, a clear-cut, complete separation of hyperthyroid and euthyroid TSH values can be achieved only if the inherent sensitivity of the TSH assay and the technical expertise of the laboratory staff are such that TSH concentrations below the normal reference interval are still reproducible with a CV of <15%. For instance, the enzyme iminunoas-say (EIA) from Abbott Laboratories as performed in our laboratory under routine conditions met the fundamental requirement for a " sensitive assay " (Figure 1), and subsequent clinical investigations have confirmed that initial conclusion. By contrast, various other TSH assays, also designated by their manufacturers as " sensitive, " have failed in our hands to meet the criteria, suggesting that they cannot be used to diagnose hyperthyroidism. Clinical experience with sensitive thyrotro-pin measurements: diagnostic and therapeutic implications. A new mono-clonal-antibody two-site solid-phase im-munoradiometric assayfor human thyrotro-pin evaluated. A new strategy for thyroid function testing. (sensitivity) for radioligand assays.its of detection and quantification, as applied to an assay for digitoxin. The photodegradation of vitamin B6 has been widely recognized and studied in considerable detail (1, 2). Since Ang (3) demonstrated that yellow incandescent or yellow fluorescent lights …