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International Classification of Diseases coding changes lead to profound declines in reported idiopathic pulmonary arterial hypertension mortality and hospitalizations: implications for database studies

Link J, Glazer C, Torres F, Chin K

Chest, 2011

Abstract

BACKGROUND: Database studies have reported several associations between the diagnosis of idiopathic pulmonary arterial hypertension (IPAH) and mortality attributable to IPAH, including older age, black race, and diabetes.

METHODS: We investigated reported deaths and hospital discharges coded as IPAH and compared these with other forms of pulmonary hypertension. Three databases were used: the US National Center for Health Statistics database (1979-2006), queried for mortality data; the Nationwide Inpatient Sample database (1993-2007), queried for hospital discharge data; and the University of Texas Southwestern Hospital-Zale Lipshy discharge database (1999, 2002).

RESULTS: Marked increases in mortality attributable to IPAH and to pulmonary hypertension (all codes combined) generally were reported from 1979 until 2002 in the National Center for Health Statistics database. In 2003, reported IPAH mortality fell sharply while total pulmonary hypertension deaths increased. The Nationwide Inpatient Sample database showed a similar pattern of changes beginning approximately 2 years earlier. In both cases, the timing of these observations corresponded with changes made to the International Classification of Diseases (ICD) coding system in use for pulmonary hypertension in that particular database. Review of pulmonary hypertension discharge data from the University of Texas Southwestern Hospital-Zale Lipshy showed similar changes in diagnosis code use.

CONCLUSIONS: Sudden shifts in…

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