Increasing incidence of necrotizing fasciitis in New Zealand: a nationwide study over the period 1990 to 2006.

OBJECTIVES: Because of concerns following necrotizing fasciitis (NF) reports in the media, we aimed to describe the incidence, mortality, case fatality and distribution of NF in New Zealand (NZ).

METHODS: By using International Classification of Disease codes to identify NF cases we analyzed the national hospital discharge and mortality data and reviewed 299 charts from 8 hospitals. The sensitivity and positive predictive value (PPV) of the hospital discharge data were calculated by comparing with the mortality dataset and chart review finding respectively.

RESULTS: Between 1990 and 2006 there was a highly significant rise in annual incidence and mortality rates of NF from 0.18 to 1.69 and from 0 to 0.3 per 100,000 person-years respectively. The causes of this increase are unknown, and were not related to 2004 coding changes for NF. Hospital discharge data had a PPV of 82.6% and sensitivity of 76.8%. The case fatality was 20.8%. Disease risk was highest in the elderly, males, and Pacific and Maori populations.

CONCLUSIONS: These findings suggest that incidence and mortality of NF are increasing in NZ. Further work is needed to investigate the causes of this increase and the marked ethnic inequalities in disease rates, particularly factors that may be preventable.