Patient pools and the use of "patient means" are valuable tools in quality control illustrated by a bone-specific alkaline phosphatase assay.

Background: Quality control (QC) is an essential part of clinical biochemistry to ensure that laboratory test results are reliable and correct. Those tests without a defined reference method constitute a special challenge, as is the case with bone-specific alkaline phosphatase (BAP).

Methods And Results: The present study reports an example where a shift in a BAP assay was detected by use of a patient pool and supported by a retrospective calculation of "patient mean", while the external QC and specific assay control material were unaffected by the shift.

Conclusions: Patient pools and the use of patient means remain a useful and inexpensive procedure for internal QC.