Red Cell Histograms and Spurious Parameters in Anemia – Study of Diagnostic Utility of Autoanalyzer Results

Abstract

BACKGROUND: Red blood cell (RBC) histograms generated by automated hematology analyzers have shown characteristic patterns useful in identifying the different red cell populations and give diagnostic clues. Although the analyzer results are precise, spurious results have been reported owing to preanalytical and analytical variables which warrant the evaluation of validity of other parameters. AIMS: The study was meant to evaluate the diagnostic utility of red cell indices and histograms in the morphological diagnosis of anemia and to interpret the spurious values generated by autoanalyzers. SETTINGS AND DESIGN: A retrospective cross-sectional study was undertaken including 917 cases of anemia. MATERIALS AND METHODS: The histograms and the red cell indices generated by autoanalyzer Mindray CAL-6000 were studied in all cases and correlated with peripheral smear. STATISTICAL ANALYSIS USED: Analysis was done using Mann–Whitney U-test for medians and interquartile range of numerical variables and Chi-square test/Fisher’s exact test for categorical variables. RESULTS: Characteristic patterns were observed in histograms such as left shift, right shift, and bimodal peaks in microcytic hypochromic anemia, macrocytic anemia, and dimorphic anemia, respectively. Spurious parameters in the study comprised high red cell indices, low RBC count, hemoglobin, and hematocrit mismatch in cases of autoimmune hemolytic anemia. Spuriously high mean corpuscular volume was associated with reticulocytosis. In vitro hemolysis was identified by factitious thrombocytosis with abnormal platelet and RBC histograms. CONCLUSION: Histograms when combined with red cell indices are of practical utility in differentiating the various morphologic types of anemia and are speculative in alerting the hematologists about the spurious parameters, forming an indispensable diagnostic tool.