Automatic wedge smears preparation may cause traumatic morphological changes in peripheral blood cells

Performance evaluation of leukocyte differential on the hematology analyzer Celltac G compared with two hematology analyzers, reference flow cytometry method, and two manual methods

BACKGROUND

The automated hematology analyzer Celltac G (Nihon Kohden) was designed to improve leukocyte differential performance. Comparison with analyzers using different leukocyte detection principles and differential leukocyte count on wedge film (Wedge-Diff) shows its clinical utility, and comparison with immunophenotypic leukocyte differential reference method (FCM-Ref) shows its accuracy performance.

METHODS

For method comparison, 598 clinical samples and 46 healthy volunteer samples were selected. The two comparative hematology analyzers (CAAs) used were XN-9000 (Sysmex) and CELL-DYN Sapphire (Abbott). The FCM-Ref provided by the Japanese Society for Laboratory Hematology was selected, and a flow cytometer Navios (Beckman-Coulter) was used. In manual differential, two kinds of automated slide makers were used: SP-10 (Sysmex) for wedge technique and SPINNER-2000 (Lion-Power) for spinner technique. The spinner technique avoids the issue of Wedge-Diff smudge cells by removing the risk of breaking cells and non-uniformity of blood cell distribution on films (Spinner-Diff).

RESULTS

The Celltac G showed sufficient comparability (r = 0.67-1.00) with the CAAs for each leukocyte differential counting value at 0.00-40.87(10⁹ /L), and sufficient comparability (r = 0.73-0.97) with FCM-Ref for each leukocyte differential percentage at 0.4-78.5. The identification ratio of the FCM-Ref in CD45-positive cells was 99.7% (99.4% to 99.8%). Differences were found between FCM-Ref/Celltac G/XN-9000/Spinner-Diff and Wedge-Diff for monocytes and neutrophils. The appearance ratio of smudge cells on wedge and spinner film was 12.5% and 0.5%.

CONCLUSION

The Celltac G hematology analyzer's leukocyte differential showed adequate accuracy compared with the CAAs, FCM-Ref, and two manual methods and was considered suitable for clinical use.

Short preheating at 41°C leads to a red blood cells count comparable to that in RET channel of Sysmex analysers in samples showing cold agglutination

AIMS

The presence of cold agglutinin in blood samples can cause a spontaneous agglutination of red blood cells (RBCs) when low temperature occurs. This phenomenon causes a spurious lowering of RBC count on the automated haematological analysers that are detected by incongruous values (≥370 g/L) of the mean cellular haemoglobi concentration (MCHC). A preheating at 37°C can remove the RBC agglutination generally resulting in a reliable count. It has been reported that the same result can be reached by using the optical reticulocyte (RET) channel of Sysmex analysers where the RBC count is not influenced by the presence of cold agglutinin. This study aims to evaluate these data in a larger population, with regard to environmental conditions on Sysmex analysers. We have also evaluated the influence of different thermal pretreatments on the RBC count.

METHODS

This study was performed on 96 remnants of peripheral blood samples (48 with MCHC in normal range and 48 with MCHC>370 g/L) which have been analysed in different preanalytical conditions on the Sysmex analysers.

RESULTS

A preheating of samples at 41°C for 1 min leads to a reversibility of the cold agglutination comparable to the one observed in the RET channel and yields better results compared with 37°C for 2 hours.

CONCLUSIONS

None of described procedures assure the complete cold agglutination reversibility in every case. Consequently, since the haematological analysers not yet provide reliable parameters to confirm the complete resolution of agglutination, further verification of RBC count accuracy needs to be performed.