Efficacy of RBC histogram in the diagnosis of morphological types of anaemia compared with peripheral smear

Abstract

Background: Anaemia constitutes an important diagnostic and clinical category of haematological disorders. Along with peripheral smear histogram is used to interpret the abnormal RBC morphology. The present study is to find out the efficacy of RBC histogram in diagnosis of morphological types of anaemia.

Methods: A total of 354 blood samples of adults >18 years, Hb <10 mg/dl included in the study conducted at Medical College, Kottayam. Peripheral smear evaluated for RBC morphology without referring to the histogram. RBC histogram from same sample analyzed separately. The results obtained, classified into 4 morphological types of anemia -Normocytic normochromic, microcytic hypochromic, macrocytic and hemolytic anemias. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy were calculated.

Results: The major proportion of study is in the age group of 51-70. Major morphologic type in both, is normocytic. Concordant samples for normocytic - 161, microcytic- 97, macrocytic- 7, Hemolytic- 1. Histogram show more sensitivity and less specificity for normocytic. Microcytic has less sensitivity, more specificity. Macrocytic showed >90% sensitivity and specificity. Hemolytic has less sensitivity, more specificity. Overall sensitivity is 75%.

Conclusions: Histogram is efficient in detecting normocytic and microcytic anaemia. In macrocytic anaemia among 40 cases detected by histogram only 7 showed concordance because histogram may detect slight variation in morphology not appreciable on light microscopy. In haemolytic anaemia only one case detected by histogram. The discordance is due to low sample size.