Sensitivity and Specificity of Mean Corpuscular Hemoglobin (MCH): For Screening Alpha-thalassemia-1 Trait and Beta-thalassemia Trait
Savitree Pranpanus MD*, Supatra Sirichotiyakul MD*, Kasemsri Srisupundit MD*, Theera Tongsong MD*
Affiliation : * Department of Obstetrics and Gynecology, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
Objective : To evaluate sensitivity, specificity, and positive and negative predictive value of mean corpuscular
hemoglobin (MCH) for screening alpha-thalassemia-1 trait and beta-thalassemia trait
Material and Method: Descriptive analysis, diagnostic test, was conducted on 396 pregnant women attending
the antenatal clinic between September 2007 and June 2008. Blood samples were collected from pregnant
women after counseling and getting informed consent. MCH was measured in all samples by automated
hematology analyzer. Determination of HbA2 level for diagnosis of beta-thalassmia trait and PCR for alpha-
thalassemia-1 gene (SEA type) were performed in all cases as a gold standard. The data were collected and
analyzed for sensitivity, specificity, and positive and negative predictive value of MCH for screening alpha-
thalassemia-1 trait and beta-thalassemia trait.
Results : Based on the ROC curve, the best cut-off level of MCH in predicting the thalassemia carriers was 26.5
picrograms. Positive MCH (< 26.5 picrograms) gave the sensitivity of 95.2% and specificity of 82.3% in
screening alpha-thalassemia-1 trait and beta-thalassemia trait. The positive predictive value and negative
predictive value were 40.4% and 99.3% respectively.
Conclusion : MCH is a good tool for screening alpha-thalassemia-1 trait and beta-thalassemia trait during
pregnancy because of its simplicity, low cost, (when determined as a part of complete blood count), and high
sensitivity.
Keywords : Erythrocyte indices, Alpha-Thalassemia, Beta-Thalassemia
