A novel point-of-care device accurately measures thyrotropin in whole blood, capillary blood and serum

Abstract

Objectives: Point-of-care (POC) measurement of thyrotropin (TSH) may facilitate prompt diagnosis of thyroid dysfunction. We evaluated the analytical performance of a new POC TSH assay (Wondfo).

Methods: TSH measurements were made from 730 consecutive, unselected subjects in an outpatient setting, using Wondfo in whole blood, capillary blood and serum or automated reference equipment (serum only).

Results: TSH measurements were user-independent. 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. Linearity was very good. Recovery rate was 97-127%. Prolongation of incubation time increased TSH results of 12% (13%) and 33% (35%) after 2 and 5 additional minutes in serum (blood), respectively. When measured simultaneously in two 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. TSH measurements between Wondfo and reference correlated strongly (r=0.93-0.96), though TSH measurements were lower with Wondfo (slopes of plots of measurements made using the two devices were 0.94 [serum vs. serum]; 0.83 [whole blood vs. serum] and 0.64 [capillary blood vs. serum]). Depending on sample material, TSH in capillary blood was lower vs. whole blood (slope: 0.82) and for whole blood vs. serum (Wondfo and reference method; slope: 0.69 and 0.83). Total haemolysis, but not elevated bilirubin or lipemia, disrupted TSH measurement.

Conclusions: The Wondfo system was straightforward to use without need for specialist technicians and demonstrated analytic performance suitable for clinical use for the diagnosis of thyroid dysfunction.

Keywords: hyperthyroidism; hypothyroidism; point-of-care testing; thyrotropin.