Measurement accuracy evaluation of urinary Mandel acid by restricted maximum likelihood method

Abstract

Currently, urinary Mandel acid is measured using several high-performance liquid chromatography (HPLC) analytical instruments. As for precision management data, it is difficult to estimate precision values such as instrument-to-instrument precision, day-to-day precision, repeat precision, and intermediate precision by nested analysis of variance owing to missing values (operation of a part of analytical instruments). Thus, we tried the restricted maximum likelihood (REML) method, which can be used for the simultaneous estimation of multiple errors from missing values. The REML method can be used to estimate instrument-to-instrument precision, day-to-day precision, repeat precision, and room precision. The intermediate precision values of low control (0.30 g/L）and high control (0.96 g/L) were less than 2.0%. From the above experiments, the REML method was confirmed to be effective for the urinary Mandel acid assay.