Optimization of a Screening Method for Macroprolactinemia.

Abstract Objective To optimize a screening method for macroprolactinemia and improve the accuracy of free prolactin (freePRL) detection. Method: Overall efficiency, calculated as the product of the immunoglobulin G (IgG) precipitation rate and the freePRL recovery rate were employed to determine the concentration of the precipitant polyethylene glycol (PEG). Then, an optimized screening method for macroprolactinemia was established. The concentrations of freePRL, obtained by gel filtration chromatography (GFC), from 66 cases were used as the gold standard, and the sensitivity, specificity, accuracy and precision of the optimized and traditional methods for detecting macroprolactinemia were compared. Results: (1) The IgG precipitation rate increased with increasing PEG6000 concentration, and the freePRL recovery rate decreased with increasing PEG6000 concentration; the overall efficiency first increased and then decreased. When the IgG concentrations in the mixture were 10 g/L, 25 g/L and 40 g/L, the concentrations of PEG6000 with the highest overall efficiency were 24%, 20% and 18%, respectively. (2) The effect of high and low IgG on the overall efficiency was 4.7% when using 20% PEG6000, which was lower than the effects when using 18% or 24% PEG6000 (9.2% and 13.2%). (3) In the optimized method established using 20% PEG6000, the macroprolactin (macroPRL) chromatographic peak disappeared, but the freePRL chromatographic peak was retained. The sensitivity of this macroprolactinemia screening method was 96.7%, and the specificity was 100%. (4) The freePRL concentrations obtained by the optimized method for samples from 30 macroprolactinemia cases and 36 true hyperprolactinemia cases were 15.8 (10.2-21.4) ng/mL and 60.2 (51.8-79.9) ng/mL; the concentrations were similar to those obtained using the GFC method (16.3 (11.9-27.2) ng/mL and 68.1 (49.5-92.9) ng/mL, respectively (p > 0.05)) and higher than those obtained using the traditional method (9.1 (6.1-17.6) ng/mL and 51.4 (43.7-71.9) ng/mL), respectively, p