Comparing the National Death Index and the Social Security Administration's Death Master File to Ascertain Death in HIV Surveillance

New York City (NYC) maintains a population-based registry of people with human immunodeficiency virus (HIV) infection to monitor the epidemic and inform resource allocation. We evaluated record linkages with the National Death Index (NDI) and the Social Security Administration's Death Master File (SSDMF) to find deaths occurring from 2000 through 2004. We linked records from 32,837 people reported with HIV and not previously known to be dead with deaths reported in the NDI and the SSDMF. We calculated the kappa statistic to assess agreement between data sources. We performed subgroup analyses to assess differences within demographic and transmission risk subpopulations. We quantified the benefit of linkages with each data source beyond prior death ascertainment from local vital statistics data. We discovered 1,926 (5.87%) deaths, which reduced the HIV prevalence estimate in NYC by 2.03%, from 1.19% to 1.16%. Of these, 458 (23.78%) were identified only from NDI, and 305 (15.84%) only from SSDMF. Agreement in ascertainment between sources was substantial (kappa = [K] 0.74, 95% confidence interval [CI] 0.72, 0.76); agreement was lower among Hispanic people (K = 0.65, 95% CI 0.62, 0.69) and people born outside the U.S. (K = 0.60, 95% CI 0.52, 0.68). We identified an additional 13.62% of deaths to people reported with HIV in NYC; white people and men who have sex with men were disproportionately likely to be underascertained without these linkages (p