Endocrine Abstracts

Objective: Point-of-care (POC) technologies, where the sample collection and biomarker measurement are undertaken immediately can reduce turnaround times for such measurements to a period of minutes and facilitate prompt diagnosis of e.g. thyroid dysfunction. This streamlined process is especially useful in the primary care setting, and in resource-poor environments such as developing countries, where recalling patients to receive their diagnosis can be challenging. To realize this potential, POC systems must perform to a level consistent with corresponding central lab-based systems. We have prospectively evaluated the analytical performance and clinical utility of a new, rapid POC thyrotropin (TSH) assay (Wondfo).

Methods: TSH concentration was measured in serum, whole blood and capillary blood using Wondfo or with two automated reference analyser platforms (serum only, Abbott TSH Alinity I and Roche Cobas e411). For Wondfo, 75 µl of the drawn blood sample are required, which are transferred on the test stripe for a 15-minute incubation, only. TSH levels are shown by the signal intensity of fluorescence-labelled detector antibodies.

Results: Seven hundred thirty consecutive, unselected outpatients (median age 46 years, 572 women) with various autoimmune and non-autoimmune thyroid diseases were included. Three hundred eighty-two subjects, 218, and 130 were euthyroid, hypothyroid, and hyperthyroid, respectively. TSH measurements were user-independent. Linearity was very good and recovery rate was 97–127%. When measured simultaneously in two POC Wondfo devices, the slope of the regression line was 1.03 (serum) and 1.02 (blood), with Spearman’s correlation of 0.99 for both. Total intra-and inter-assay variation [CV%] was 12.1% and 16.2%, respectively. Total CV% was 10.6-22.6% and 14.5-21.6% in serum and whole blood, respectively. TSH measurements between the POC assay and the reference analysers correlated strongly (r = 0.93–0.96). There was no relevant influence of the user-performance on the POC device. The CVs were 13% and 17% in serum and potassium-EDTA whole blood, respectively, and were within the range expected from the overall CVs of the POC device. Prolongation of incubation time increased TSH results of 12% (13%) and 33% (35%) after two and five additional minutes in serum (blood), respectively. Total haemolysis, but not elevated bilirubin or lipemia, disrupted TSH measurement.

Conclusions: For the first time, a POC system, which accurately measures TSH from three commonly used matrices is introduced. This rapid POC device was straightforward to use without need for specialist technicians and demonstrated user-independent analytic performance very suitable for clinical diagnosis and differential diagnosis of thyroid dysfunction.