Interventional surveillance of rare diseases: New York State's experience with CJD

Abstract

An accurate diagnosis is important in disease surveillance but is particularly so for rare diseases; inclusion or exclusion of one or two patients from analysis can influence incidence or mortality rates greatly. Since CJD and vCJD can only be definitively diagnosed with specialized testing of brain tissue at the National Prion Disease Pathology Surveillance Center (NPDPSC), actions were undertaken to improve diagnosis. Previous surveillance of CJD was passive, using mortality records and hospital discharge data to identify potential CJD patients. To improve autopsy rates and encourage use of NPDPSC services required active surveillance, learning of possible CJD patients prior to death. A survey of neurologists and pathologists was conducted to understand barriers to autopsy and guide interventional surveillance. An interdisciplinary workgroup was also established to develop additional intervention strategies. In 2000, 84% of suspected instances of CJD were identified passively. In contrast, by 2004, 71% of patients suspected of CJD were actively reported. Rates of autopsy and/or biopsy for patients suspected of CJD increased from 44% in 2000 to 60% in 2004. Diagnostic certainty also increased. The proportion of patients with possible or probable CJD declined with interventional surveillance (from 46% in 2000 to 31% in 2003), while the proportion ruled out or unfounded cases more than doubled from 14% in 2000 to 36% in 2003. Improvements in timeliness of reporting led to greater ability to intervene to improve accuracy of CJD diagnosis. Interventional surveillance is labor intensive but provides a stronger base upon which to conduct descriptive epidemiology of a rare disease of public health significance.