Clin Biochem Rev 2008; 29 Supplement(i):S27-S31

Use of Capability Index to Improve Laboratory Analytical Performance

Renze Bais
Pacific Laboratory Medicine Services (PaLMS), Northern Sydney Central Coast Health, Royal North Shore Hospital, St Leonards,
Sydney, NSW 2065, Australia.
For correspondence: Dr Renze Bais e-mail: rbais@med.usyd.edu.au

Summary
• For detection of errors where the standard deviation is wide compared to clinical requirements, consider use of the Capability
Index (Cps).
• Cps is defined as ‘Allowable Limit of Error divided by the standard deviation of between-batch QC measurement’.
• ‘Capable’ assays have Cps >4 compared with ‘incapable’ ones with Cps <4.
• Capability of an analyte can be used to optimise the amount of quality control (QC) required and still maintain appropriate
error detection.
• For EQA material, Cps can be used for continuously monitoring individual analytes, comparing laboratory performance
with peers and comparison with industry-wide performance.
• The capability approach can result in reducing the number of QCs run per day, reducing costs as well as significantly
improving the performance of a number of assays.