Double-module ratio as a patient-based real-time quality control index for small shift detection and comparative assay.

Abstract

Objectives: Irregular fluctuations in patient data affect patient-based real-time quality control (PBRTQC) performance. Moreover, results among multiple instruments can be inconsistent. Here, we explored a simple index, double-module ratio, to improve PBRTQC performance through overcoming irregular fluctuations, and ensure consistency across multiple instruments in real time.

Methods: Laboratory results from the same departments tested centrally such that the original patient data fluctuated irregularly during the day were included. Albumin (Alb), calcium (Ca), cholinesterase (ChE), and total protein (TP) indexes derived from a single module were processed through conventional PBRTQC. The ratios calculated from PBRTQC data of two modules were defined as double-module ratios (R_Alb, R_Ca, R_ChE, and R_TP). The four index pairs were compared using various PBRTQC procedures, including conventional algorithms: moving average (MA), moving median, exponentially weighted MA, and moving standard deviation.

Results: All four ratios (R_Alb, R_Ca, R_ChE, and R_TP) were more powerful in identifying system error (SE) than their counterparts (Alb, Ca, ChE, and TP). These improvements were proportional to the degree of reduction in QC data variation after ratios were taken. In particular, R_Alb, R_Ca, and R_TP could aid in detecting small SEs (about <1.5 folds of the allowable total errors) significantly. Although ChE demonstrated almost no surveillance capacity for negative SEs, R_ChE demonstrated a significant improvement. The impact of the ratios on random error detection was dependent on the indexes and PBRTQC parameters.

Conclusions: As a PBRTQC index, double-module ratios can facilitate small shift detection and ensure result consistency among various modules in real time.