An algorithm to aid in the investigation of thalassemia trait in multicultural populations

Context.-The differentiation between iron deficiency and a thalassemia synd rome is an important consideration in the investigation of microcytic anemi a. Objective.-An established statistical method was used to demonstrate the im portance of considering ethnic background in combination with mean cell vol ume (MCV) in the investigation of P-thalassemia trait in a multicultural ur ban population. Design.-Posttest probabilities for beta-thalassemia trait were calculated u sing likelihood ratios for various microcytic MCV ranges in conjunction wit h published pretest probabilities for beta-thalassemia trait based on ethni c background. Setting.-Regional hemoglobinopathy laboratory, St Joseph's Hospital, Hamilt on, Ontario, Canada. Patients.-Patient data were derived from a previously published study. The original study cohort consisted of 789 patients aged 18 years or older who had an MCV less than 80 fL and were referred for routine complete blood cou nt during a 6-month period. Main Outcome Measures.-Posttest probabilities. Results.-Simplified tables for the determination of posttest probabilities for beta-thalassemia trait in individual patients based on ethnic backgroun d and MCV are provided. An algorithm to assist in determining when thalasse mia investigations are indicated is presented. Conclusions.-A high index of suspicion based on ethnic background and low M CV can provide increased sensitivity and specificity for the detection of t halassemia trait in centers with multicultural populations similar to the s tudy population.