Differential Diagnosis of Anemia Using the Erythrocyte Filterability Method

Hereditary hemolytic anemias (HHAs) have quite similar clinical manifestations, complicating differential diagnosis and determining treatment, such as splenectomy. For the differential diagnosis of hereditary spherocytosis (HS), pyruvate kinase deficiency (PKD), and hereditary stomatocytosis (HSt), we proposed to measure erythrocyte filterability through membrane filters with a pore diameter of 3 or 3.5 μm. Our modified method provides improved reproducibility reducing the variation in results caused by differences in the filters used. The filterability of erythrocytes significantly differs in patients with HS, HSt and PKD (medians and 1.5 IQR were: 0.045 [0; 0.51] (n=88); 0.685 [0.46; 0.79] (n=12) and 0.75 [0.55; 0.86] (n=28) rel. un., respectively). The specificity of the filterability test for HS diagnosis was 100%, comparable to the best available tests, while its sensitivity (85.2%) was somewhat lower than that of some alternative methods. Only the filterability test could identify a second subgroup in HS patients (14.8%) with higher filterability (close to normal), but their HS diagnosis was confirmed by the decreased filterability by 3-µm pore filter. This subgroup requires further detailed study. The proposed filterability measurement method is promising for diagnosing HS. It has high sensitivity and specificity and can be performed quickly without expensive equipment.