Table 1_Strengthening the interpretation of longitudinal EQA data through the sporadic inclusion of native human sera in general clinical chemistry.xlsx

An exception among native EQAMs was observed for GGT, showing differences in bias of more than −7% and pronounced variabilities in MP-specific mean bias (standard deviation (SD) in percentage points: 3.9–10.2), likely associated with low enzyme activities. In contrast, most analyte/MP-specific bias in native EQAMs was highly consistent (SD: enzymatic assays 0.3–3.1, creatinine (kinetic) 1.7–6.6, sodium 0.21–0.42). Longitudinal data showed higher variabilities for processed EQAMs for multiple analyte/MP pairings (SD: enzymatic assays 1.0–10.0, creatinine (kinetic) 2.1–6.5, sodium 0.38–1.00), indicating higher MP susceptibilities to synthetic EQAM matrices.

Substantial shifts in bias ranges between sample types were observed for cholesterol and urea across most MPs, and for individual MPs for the remaining analytes.</p>Conclusion<p>In some processed EQAM batches, bias was markedly greater than observed for the batches in the comparative EQA survey, indicating that the limited number of batches in such studies do not allow generalized interpretation on commutability, and requires batch-specific assessment.

However, when combined with longitudinal monitoring of MP-specific bias, a comprehensive picture emerges of MP trueness, MP susceptibility to interferences and commutability of EQAMs, thereby supporting MP and control material manufacturers in quality improvement.</p>