The influence of age, sex, and race on the upper reference limit of serum C-reactive protein concentration.

OBJECTIVE: The recommended reference range for serum C-reactive protein (CRP) concentrations is usually not adjusted for age and sex. We sought to determine if age, sex, and race or ethnicity influence the distribution of CRP values, and if upper reference limits of CRP should be adjusted by demographic factors. METHODS: Interviews, physical examinations, and blood draws were performed on > 22,000 individuals age > or = 4 yrs representative of the noninstitutionalized population of the United States, as part of the Third National Health and Nutrition Evaluation Survey (NHANES III). Serum CRP concentrations were measured by nephelometric immunoassay. RESULTS: The 95th percentile value of CRP in the overall population was 0.95 mg/dl for males and 1.39 mg/dl for females, and varied with age and race. For ages 25-70 yrs, the age adjusted approximate upper reference limit (mg/dl) was CRP = age/50 for males, and CRP = age/50 + 0.6 for females. The upper limits for Mexican-Americans and non-Hispanic whites were similar, whereas for non-Hispanic black adults the approximate upper limit was CRP = age/30 for males and CRP = age/50 + 1.0 for females. Even after accounting for identified inflammatory conditions, demographic factors influenced the reference limits of CRP. The 95th percentile values were uniformly lower in children than in older adults. CONCLUSION: Demographic factors, including age, sex, and race, should be used to adjust the upper reference limit for CRP. Clinicians should be aware of these factors when using CRP values to assess inflammatory diseases.

Update on the seroepidemiology of human immunodeficiency virus in the United States household population: NHANES III, 1988-1994.

To update the estimate of seroprevalence of HIV from the third National Health and Nutrition Examination Survey (NHANES III), data from the second phase of the survey were combined with previously published data to produce a more precise estimate. The testing was performed anonymously on 11,203 individuals 18-59 years of age examined from 1988 to 1994. Fifty-nine individuals were HIV positive, for an overall prevalence of 0.32%. The number of individuals living in households with HIV infection based on this estimate was 461,000, with a 95% confidence interval of 290,000-733,000. Analysis of nonresponse demonstrated that white and black men 40-59 years of age were least likely to participate in the survey. A sensitivity analysis demonstrated that this nonresponse may have biased the NHANES III estimate downward by 190,000 persons. Data from the second phase of the survey were used to analyze the association between drug use and HIV infection. Black women who used cocaine were 12 times more likely to be HIV positive compared with all tested black women (6.5% vs. 0.55%). This survey provides an estimate of HIV prevalence for individuals who reside in households but excludes some persons who are at higher risk for HIV infection, including prisoners and the homeless not residing in shelters.