Manual slide review (MSR) is usually triggered by the results of automated hematolgy analyzers, but each laboaratory has different ciriteria for MSR. This study was carried out to investigate the current status of MSR criteria of automated complete blood cell count (CBC) and white blood cell (WBC) differential results and to propose a basic guideline for MSR.

Total 111 laboratories were surveyed regarding MSR using questionnaires. The questionnaire asked: kinds of automated hematology analyzers used and the presence of criteria triggering MSR in seven categories: 1) CBC results, 2) 5 differential WBC counts, 3) 3 differential WBC counts, 4) automated reticulocyte counts, 5) delta check, 6) instrument flags (or messages), 7) clinical information (wards or diseases). Based on the survey results, we determined basic and extended criteria for MSR. With these criteria, we consulted nine hematology experts to get a consensus.

All 111 laboratories had their own MSR criteria. Among 111 laboratories, 98 (88.3%) used more than three criteria for MSR including CBC results and 5-part WBC differential count results and 95 (85.6%) had criteria of flags triggering MSR. For MSR criteria with numeric values, the 10th, 50th, and 90th percentiles of upper and lower threshold values were obtained. The basic guideline for MSR was made.

We proposed a basic guideline for MSR. This guideline would be helpful to hematology laboratories for their daily operation and providing more rapid and accurate CBC and WBC differential results.