Screening for hereditary spherocytosis by use of automated erythrocyte indexes.

OBJECTIVE

To determine whether the mean corpuscular hemoglobin concentration (MCHC) or other erythrocyte indexes, as determined by automated cell counters, remains a useful screening test for identifying patients with hereditary spherocytosis (HS).

METHODS

Erythrocyte indexes from 112 children with HS who had not undergone splenectomy were compared with those measured in an equal number of healthy, age-matched children. All indexes were derived from measurements obtained by aperture impedance.

RESULTS

Mean corpuscular hemoglobin concentration in the HS group was 35.9 gm/dl, significantly higher than in normal control subjects (34.3 gm/dl; p < 0.001). Mean erythrocyte distribution width also was significantly higher in patients with HS (19.3 vs 12.6; p < 0.001). The MCHC distinguishes individuals with HS, with an area under the receiver operating characteristic curve of 0.86. Although not disease specific, an erythrocyte distribution width > 14 has 85% sensitivity and 97% specificity and an area under the receiver operating characteristic curve of 0.92. An MCHC > 35 gm/dl has a sensitivity of 70% and a specificity of 86%. Combining the MCHC and erythrocyte distribution width increases the area under the receiver operating characteristic curve to 0.97. Specificity is 100% and likelihood ratio is infinite when both the MCHC and erythrocyte distribution width are elevated.

CONCLUSIONS

The automated MCHC is an effective screening test to identify children with HS. An elevated erythrocyte distribution width adds additional specificity and is itself a powerful screening tool. The combination of the two tests is an excellent predictor for the diagnosis of HS.