Abstract
OBJECTIVE: To determine the reliability of the Social Security Death Master File (DMF) after the November 2011 changes limiting the inclusion of state records. DATA SOURCES: Secondary data from the DMF, New York State (NYS) and New Jersey (NJ) Vital Statistics (VS), and institutional data warehouse. STUDY DESIGN: Retrospective study. Two cohorts: discharge date before November 1, 2011, (pre-2011) or after (post-2011). Death in-hospital used as gold standard. NYS VS used for out-of-hospital death. Sensitivity, specificity, Cohen's Kappa, and 1-year survival calculated. DATA COLLECTION METHODS: Patients matched to DMF using Social Security Number, or date of birth and Soundex algorithm. Patients matched to NY and NJ VS using probabilistic linking. PRINCIPAL FINDINGS: 97 069 patients January 2007-March 2016: 39 075 pre-2011; 57 994 post-2011. 3777 (3.9 percent) died in-hospital. DMF sensitivity for in-hospital death 88.9 percent (κ = 0.93) pre-2011 vs 14.8 percent (κ = 0.25) post-2011. DMF sensitivity for NY deaths 74.6 percent (κ = 0.71) pre-2011 vs 26.6 percent (κ = 0.33) post-2011. DMF sensitivity for NJ deaths 62.6 percent (κ = 0.64) pre-2011 vs 10.8 percent (κ = 0.15) post-2011. DMF sensitivity for out-of-hospital death 71.4 percent pre-2011 (κ = 0.58) vs 28.9 percent post-2011 (κ = 0.34). Post-2011, 1-year survival using DMF data was overestimated at 95.8 percent, vs 86.1 percent using NYS VS. CONCLUSIONS: The DMF is no longer a reliable source of death data. Researchers using the DMF may underestimate mortality.