Plasma sFcγRIII levels (AU) in neutropenic patients with (n = 14) or without infections (n = 28) in the period 3 months before to 3 months after a single sFcγRIII measurement. Each patient with an infection was matched with two patients without infections who had approximately the same neutrophil count. The mean sFcγRIII levels (± standard deviation [SD]) in patients with and without infections were 54 ± 26 AU and 113 ± 63 AU, respectively (Welch's approximate t test; two-tailed P value = .0002). No statistically significant differences were observed between the two groups regarding sex and age distribution. FcγRIIa-131R/H and FcγRIIIb-NA(1,2) phenotype distributions were similar in the two groups (3 × 2 contingency table; P = .91 and P = .53, respectively).