RESUMEN
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.
RESUMEN
BACKGROUND: Labile iron pool (LIP) is intracellular nonprotein bound iron that can generate oxygen radicals via the Fenton reaction resulting in oxidative cell damage. Therefore, quantitative measurement of LIP will be helpful for detecting and monitoring the toxic iron status in iron overloaded patients. This study demonstrated LIP level and its correlation to oxidative stress status in ß-thalassemic erythrocytes. METHODS: LIP and reactive oxygen species (ROS) level, numbers of erythrocyte vesicles and apoptosis were assayed by flow cytometric methods in 30 blood samples from ß-thalassemia/hemoglobin E patients and 17 blood samples from healthy volunteers with normal hemoglobin type. RESULTS: ß-thalassemic erythrocytes showed higher LIP level, defined as the difference in calcein fluorescent intensity of the cells treated with or without deferiprone, than normal erythrocytes (mean ± 2SD as 62.39 ± 39.58 versus 44.65 ± 35.86, P = 0.003). The LIP level above 67, a cutoff value of LIP level obtained from receiver operating characteristic curve analysis, had a significant positive correlation with oxidative stress status for ROS level (r = 0.90, P < 0.001) and also the amount of erythrocyte vesicles (r = 0.79, P = 0.002). In contrast, the LIP level showed a significant negative correlation with the patients' hemoglobin level (r = -0.66, P = 0.028). CONCLUSIONS: The LIP assay is suggested as an alternative test to monitor the magnitude of iron overload and its consequent oxidative stress in ß-thalassemia. LIP level may also be used as a marker for therapeutic response to iron chelation treatment. © 2018 International Clinical Cytometry Society.
