Between and within calibration variation: implications for internal quality control rules

Chun Yee Lim, Jermyn Jit Siong Lee, Kay Weng Choy, Tony Badrick, Corey Markus, Tze Ping Loh

Research output: Contribution to journalArticlepeer-review

2 Citations (Scopus)

Abstract

The variability between calibrations can be larger than the within calibration variation for some measurement procedures, that is a large CVbetween:CVwithin ratio. In this study, we examined the false rejection rate and probability of bias detection of quality control (QC) rules at varying calibration CVbetween:CVwithin ratios.

Historical QC data for six representative routine clinical chemistry serum measurement procedures (calcium, creatinine, aspartate aminotransferase, thyrotrophin, prostate specific antigen and gentamicin) were extracted to derive the CVbetween:CVwithin ratios using analysis of variance. Additionally, the false rejection rate and probability of bias detection of three ‘Westgard’ QC rules (2:2S, 4:1S, 10X) at varying CVbetween:CVwithin ratios (0.1–10), magnitudes of bias, and QC events per calibration (5–80) were examined through simulation modelling. 

The CVbetween:CVwithin ratios for the six routine measurement procedures ranged from 1.1 to 34.5. With ratios >3, false rejection rates were generally above 10%. Similarly for QC rules involving a greater number of consecutive results, false rejection rates increased with increasing ratios, while all rules achieved maximum bias detection.

Laboratories should avoid the 2:2S, 4:1S and 10X QC rules when calibration CVbetween:CVwithin ratios are elevated, particularly for those measurement procedures with a higher number of QC events per calibration.

Original languageEnglish
Pages (from-to)525-530
Number of pages6
JournalPathology
Volume55
Issue number4
Early online date16 Feb 2023
DOIs
Publication statusPublished - Jun 2023

Keywords

  • Calibration
  • laboratory management
  • precision
  • quality control

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