Comparison between optical microscopy and the Sysmex XN‐3000 for schistocyte determination in patients suspected of having schistocytosis

Abstract

Background and aims Diagnosis of thrombotic microangiopathy (TMA) relies on microscopic schistocyte determination by an experienced microscopist. In addition, schistocytes can be found in non‐TMA–related disorders such as thalassaemia. We aimed to compare the accuracy of the automated haematology analyser Sysmex XN‐3000 for schistocyte detection, to that of the microscopy approach, in patients suspected of having schistocytosis. Methods Consecutive blood samples were collected between April 2016 and March 2017 at Siriraj Hospital, Mahidol University, Bangkok, Thailand. Specimens were collected from adults with suspected TMA or with thalassaemia trait and/or disease. All blood samples were examined by both microscopy and the analyser. Samples were considered to be positive for schistocytes (ie, schistocytosis) if they had a schistocyte count ≥1% by microscopy. The analyser's ability to determine schistocytosis was assessed by receiver operating characteristic (ROC) curve. Sensitivity, specificity, positive (PPV), and negative predictive value (NPV) of an appropriate cut‐off point were calculated, with manual microscopy as the standard. Quantitative agreement in schistocyte counts between the two approaches was assessed using 95% limits of agreement, Bland‐Altman plots, intraclass correlation coefficient, and concordance correlation coefficient. Results Ninety‐seven blood samples (62 suspected TMA and 35 thalassaemia) were collected. ROC curve analysis of the analyser for determining schistocytosis showed an area under the curve of 0.803 (95% confidence interval, 0.689‐0.917, P < 0.001). A cut‐off point of 0.6% yielded 86.1% sensitivity, 77.8% specificity, 94.4% PPV, and 56.0% NPV. The automated schistocyte count did not quantitatively agree with schistocyte counts by microscopy, neither in all blood specimens (mean of difference: −1.09; 95% limits of agreement, −11.9 to 9.7) nor in the subgroups (TMA, −0.88; 95% limits of agreement, −6.60 to 4.84; thalassaemia, −2.4; 95% limits of agreement, −14.10 to 9.30). The differences in the estimation of fragmented red blood cells between the methods tended to increase at higher schistocyte counts. Conclusion Sysmex XN‐3000 can be used for qualitative measurement of schistocytosis, but should not be used as a quantitative tool for schistocyte counting. Improvements are needed before this analyser's schistocyte detection feature can be recommended for use in clinical practice.

Low ADAMTS13 Activity Correlates with Increased Mortality in COVID-19 Patients

“…As previously reported, the sensitivity of RBC or platelet flags to detect schistocytes/RBC fragments is less than 1% (0.6-0.9%). 16 Thus, we classified all cases with no RBC/platelet flags as <1% schistocytes/RBC fragments.…”

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“…As previously reported, the sensitivity of RBC or platelet flags to detect schistocytes is less than 1% (0.6-0.9%). 15 Thus, we classified all cases with no RBC/platelet flags as <1% schistocytes. Thus, we analyzed the trends of ADAMTS13 and VWF levels stratified by D-Dimer.…”

2021 update of the 2012 ICSH Recommendations for identification, diagnostic value, and quantitation of schistocytes: Impact and revisions

“…False-negative FRC counts in samples with an increased MCV 4,60 and false-positive FRC counts due to interference with platelets are documented in the literature. [63][64][65][66] Digitized morphologic preclassification (before reclassification by an experienced morphologist) of RBCs has been evaluated in terms of the ability to identify schistocytes with reference to the 2012 ICSH reference method. 67,68 Overall, about two-thirds of RBC initially classified as schistocytes by the software had to be reclassified to other categories (false-positive cells), with a high sensitivity but relatively poor specificity.…”

“…The authors suggest that FRC count is a valuable parameter that should be included in the final blood count report because of its significant impact both for screening in neonatal coagulopathies and infections and for monitoring, thus potentially reducing serial phlebotomies. False‐negative FRC counts in samples with an increased MCV 4,60 and false‐positive FRC counts due to interference with platelets are documented in the literature 63‐66 …”