RESUMO
The purpose of this study was to examine normal serum values for the complement components, C3, C4, and C5, and total hemolytic complement (CH50) activity in 163 healthy infants and children, in the age range from birth through 14 years. There were statistically significant relationships of C3, C4, and C5, but not CH50 with age. None of the complement components or CH50 could be differentiated by sex or race. Tolerance limits for high and low values were projected for each complement measurement for 75%, 90%, and 95% of the general population. Our data confirm the differences in complement levels between children and adults and demonstrate a wide range of values within each group, reflecting the biologic variability of complement measurements. These results emphasize the importance of establishing normal pediatric values in any laboratory that measures complement profiles in various diseases of childhood.