Use of Complete Blood Cell Count Components to Screen for HS
The neonatal hereditary spherocytosis (HS) index, defined as the mean corpuscular hemoglobin concentration divided by the mean corpuscular volume, has been proposed as a screening tool for HS in neonates. In a population of mostly white infants, an HS Index more than 0.36 was 97% sensitive and more than 99% specific. Researchers evaluated the utility of the HS Index among a more racially and ethnically diverse population and determined if its discrimination varies with total serum bilirubin (TSB) levels.

Erythrocyte indices from the first complete blood count drawn at less than 7 days and TSB levels drawn at less than 30 days were obtained. Diagnoses of HS were confirmed via chart review.

--HS was confirmed in 79 infants, 1.2 per 10?000. HS was more common among infants of white and “other” race or ethnicity and among those with higher peak TSB levels.

--The area under the receiver operating characteristic curve for the HS Index was 0.84.

--Likelihood ratios ranged from 10.1 for an HS Index more than 0.380 to 0.1 for an HS Index less than 0.310.

--Dichotomized at 0.36, the HS Index was 56% sensitive and 93% specific. Discrimination of the HS Index appeared best among infants with TSB levels less than 10 mg/dL.

Conclusively, the HS Index had only a minor effect on the likelihood of HS when acquired from a CBC drawn within the first week after delivery.