Derivation and validation of the Denver Human Immunodeficiency Virus (HIV) risk score for targeted HIV screening

Abstract

Targeted screening remains an important approach to human immunodeficiency virus (HIV) testing. The authors aimed to derive and validate an instrument to accurately identify patients at risk for HIV infection, using patient data from a metropolitan sexually transmitted disease clinic in Denver, Colorado (1996-2008). With multivariable logistic regression, they developed a risk score from 48 candidate variables using newly identified HIV infection as the outcome. Validation was performed using an independent population from an urban emergency department in Cincinnati, Ohio. The derivation sample included 92,635 patients; 504 (0.54%) were diagnosed with HIV infection. The validation sample included 22,983 patients; 168 (0.73%) were diagnosed with HIV infection. The final score included age, gender, race/ethnicity, sex with a male, vaginal intercourse, receptive anal intercourse, injection drug use, and past HIV testing, and values ranged from -14 to +81. For persons with scores of <20, 20-29, 30-39, 40-49, and ≥50, HIV prevalences were 0.31% (95% confidence interval (CI): 0.20, 0.45) (n = 27/8,782), 0.41% (95% CI: 0.29, 0.57) (n = 36/8,677), 0.99% (95% CI: 0.63, 1.47) (n = 24/2,431), 1.59% (95% CI: 1.02, 2.36) (n = 24/1,505), and 3.59% (95% CI: 2.73, 4.63) (n = 57/1,588), respectively. The risk score accurately categorizes patients into groups with increasing probabilities of HIV infection.

Figure 1.

Prevalence of human immunodeficiency virus (HIV) infection within each risk score category in the derivation and validation samples, Denver, Colorado, 1996–2008 and Cincinnati, Ohio, 1998--2010. Point estimates and 95% confidence intervals are staggered for clarity. The risk score ranges from −14 to +81. Bars, 95% confidence interval.

Figure 2.

Calibration (part A) and discrimination (part B) of a risk score designed to identify patients at risk of human immunodeficiency virus (HIV) infection, Denver, Colorado, 1996–2008 and Cincinnati, Ohio, 1998--2010. The area under the receiver operating characteristic curve was 0.85 (95% confidence interval: 0.83, 0.88) in the derivation sample and 0.75 (95% confidence interval: 0.70, 0.78) in the validation sample.