CLINICAL-VALUE OF SOLUBLE IGG FC-RECEPTOR-TYPE-III IN PLASMA FROM PATIENTS WITH CHRONIC IDIOPATHIC NEUTROPENIA

Previous studies have shown that the plasma level of soluble IgG Pc re ceptor type III (sFc gamma RIII) is a measure of the total body neutro phil mass, The aim of this study was to determine whether the plasma l evel sFc gamma RIII is associated with the risk of contracting bacteri al infections in patients with neutropenia. We collected blood from 66 patients suffering from acquired idiopathic neutropenia, whose blood was sent to our laboratory for diagnostic evaluation of neutropenia (n eutrophil count <1,500 cells/mu L), Soluble Fc gamma RIII levels were measured in plasma. Genotype distibutions of Fc gamma R polymorphisms were determined. Clinical data were obtained from the patient files. P atients were assessed as to whether or not they had suffered from a ba cterial infection 3 months before to 3 months after a single sFc gamma RIII measurement. In addition, longitudinal data were obtained from 2 1 patients, Of the 66 neutropenic patients who were included, 15 had s uffered from a bacterial infection in the period 3 months before to 3 months after sFc gamma RIII measurement. The age and sex distribution was equal among the groups with and without infections, as were the ge notype frequencies of neutrophil Fc gamma R polymorphisms, Both neutro phil count and plasma level sFc gamma RIII were significantly lower in the patient group with infections, compared with the noninfected grou p (P = .03 and P < .0001, respectively), No infections were reported f or patients who had plasma sFc gamma RIII levels above 100 arbitrary u nits (AU; normal value, 30 to 200), After matching each infected patie nt with two noninfected patients having the same neutrophil count, sFc gamma RIII plasma levels remained significantly lower in the group wi th infections (P = .0001), For the patients who were followed in time, no infections were reported when sFc gamma RIII levels were above 100 AU, In conclusion, our population of patients with chronic idiopathic neutropenia with plasma sFc gamma RIII levels above 100 AU did not sh ow an increased risk of contracting bacterial infections. (C) 1998 by The American Society of Hematology.