Clinical value of smear review of flagged samples analyzed with the Sysmex XN hematology analyzer

A smear review is typically made in flagged differential counts performed with hematology analyzers although the clinical value of such reviews is uncertain. Therefore, we evaluated the differences in differential counts between Sysmex XN-9000 and a smear review in flagged samples. Furthermore, the clinical value of blasts identified was investigated.

Data on all differential counts performed in a two-year period were identified at two laboratories. In patients with blasts, the electronic health record was reviewed. Agreement between automated and manual differential counts was evaluated by Bland-Altman plots. Concordance between the two methods categorized according to reference intervals was evaluated and adjusted for irrelevant non-concordance caused by random analytical error.

In total, 5,500 flagged differential counts were identified from 4,092 patients. A good agreement between the automated and manual differential count was found for all cell types (-0.480 × 10⁹/L to 0.297 × 10⁹/L). The concordance between the two methods was excellent for all cell types, except for monocytes (82 %) where the automated estimates were higher than the manual in 19 % of samples. Blasts were identified in 241 (1 %) of smear reviews. Acute leukemia was diagnosed in 13 (5 %) patients, and only in one patient contributed the detection of blasts to the suspicion of acute leukemia.

Our findings indicate that routine smear review of all flagged samples do not contribute with additional, significant information. After local validation and dialogue with clinical departments, such reviews may potentially be omitted to increase cost-effectiveness and reduce turn-around-time.