Sir.—The study of RBCs done by Stockman and Oski (Journal 1980;134:945-946) demonstrated that mean corpuscular volume (MCV) of low-birth-weight infants progressively declined with age. No etiologic factor for this decline could be determined.
The MCV was determined by electronic counting, and therefore no distinction could have been made between reticulocytes and mature RBCs, as only an average MCV is recorded.1 Thus, a high peripheral blood reticulocyte count, as occurs normally in the perinatal period,2 may contribute to a high MCV, even though the mature RBCs may be of smaller size.
I suggest that the high values of MCV and the subsequent decline with age may be, at least in part, an artifact of electronic counting, secondary to the normal decline of the reticulocyte count in the perinatal period.
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