CONTEXT: The differentiation between iron deficiency and a thalassemia syndrome is an important consideration in the investigation of microcytic anemia. OBJECTIVE: An established statistical method was used to demonstrate the importance of considering ethnic background in combination with mean cell volume (MCV) in the investigation of beta-thalassemia trait in a multicultural urban population. DESIGN: Posttest probabilities for beta-thalassemia trait were calculated using likelihood ratios for various microcytic MCV ranges in conjunction with published pretest probabilities for beta-thalassemia trait based on ethnic background. SETTING: Regional hemoglobinopathy laboratory, St Joseph's Hospital, Hamilton, 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 count 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 background and MCV are provided. An algorithm to assist in determining when thalassemia investigations are indicated is presented. CONCLUSIONS: A high index of suspicion based on ethnic background and low MCV can provide increased sensitivity and specificity for the detection of thalassemia trait in centers with multicultural populations similar to the study population.
CONTEXT: The differentiation between iron deficiency and a thalassemia syndrome is an important consideration in the investigation of microcytic anemia. OBJECTIVE: An established statistical method was used to demonstrate the importance of considering ethnic background in combination with mean cell volume (MCV) in the investigation of beta-thalassemia trait in a multicultural urban population. DESIGN: Posttest probabilities for beta-thalassemia trait were calculated using likelihood ratios for various microcytic MCV ranges in conjunction with published pretest probabilities for beta-thalassemia trait based on ethnic background. SETTING: Regional hemoglobinopathy laboratory, St Joseph's Hospital, Hamilton, 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 count 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 background and MCV are provided. An algorithm to assist in determining when thalassemia investigations are indicated is presented. CONCLUSIONS: A high index of suspicion based on ethnic background and low MCV can provide increased sensitivity and specificity for the detection of thalassemia trait in centers with multicultural populations similar to the study population.