NEUTROPHIL NUCLEAR SEGMENTATION IN MILD COBALAMIN DEFICIENCY - RELATION TO METABOLIC TESTS OF COBALAMIN STATUS AND OBSERVATIONS ON ETHNIC-DIFFERENCES IN NEUTROPHIL SEGMENTATION

Neutrophil hypersegmentation is considered the most sensitive peripher al blood cell marker of cobalamin deficiency. However, its diagnostic value in the mild deficiency states that accompany most low cobalamin levels and its relation to metabolic tests of cobalamin status are unk nown, The authors compared neutrophil lobe averages and percent neutro phils with 5 or more lobes (%5+ lobes) in 169 subjects with their mean corpuscular volume (MCV) and serum cobalamin, methylmalonic acid (MMA ), homocysteine, and folate levels and, in 65 cases, with the deoxyuri dine suppression test (dUST). Only 9 subjects had hypersegmentation by lobe average and 20 subjects by %5+ lobes. They were not more often c obalamin-deficient than subjects without hypersegmentation. Moreover, only one of 34 subjects with dUST results diagnostic for cobalamin def iciency had neutrophil hypersegmentation, Both indices of neutrophil s egmentation in the 169 subjects correlated significantly with homocyst eine levels, They also showed weak inverse correlation with cobalamin levels, but did not correlate with MMA, folate, or MCV values. Cobalam in therapy for 6 months did not significantly change neutrophil lobe a verages in 35 subjects with mild deficiency, compared with 8 nondefici ent controls, and only marginally improved the %5+ lobes. A surprising , incidental observation was that blacks had significantly greater neu trophil segmentation by both criteria than did whites and others. This difference was unrelated to cobalamin or folate status, Our results i ndicate that dUST abnormalities precede all morphologic changes of def iciency, including hypersegmentation. Although a tendency exists for n eutrophil segmentation to increase very slightly as some serum values, especially homocysteine, start to worsen in mild cobalamin deficiency , the metabolic changes precede overt hypersegmentation. Neutrophil nu clear segmentation is insufficiently sensitive in relation to metaboli c evidence of deficiency to be used as a clinical tool in the diagnosi s of mild cobalamin deficiency.