Impact of disease severity and hematocrit level on reuse-associated mortality.

Prior studies on reuse-associated mortality have presented conflicting results and included few adjustments for disease severity or hematocrit levels. To evaluate the impact of patient and provider characteristics on reuse-associated mortality, we developed a period-prevalent model with a 6-month entry period. Five cohorts of Medicare hemodialysis patients surviving from July 1 through December 31 of the entry year (1991, 60,985 patients; 1992, 63,081 patients; 1993, 76,018 patients; 1994, 82,899 patients; 1995, 91,761 patients) were followed up for the next year. Using a basic Cox regression survival model (M-1) including age, sex, race, renal diagnosis, prior end-stage renal disease time, unit age, unit size, water treatment, dialysate, and germicide, results were compared with those using a more inclusive model (M-4) adding dialyzer type (conventional or high efficiency/high flux), unit designation (hospital based or freestanding), unit profit status, comorbidity, disease severity, and hematocrit. The previous association of for-profit units with increased mortality was not present after 1994. Whereas the M-1 analysis showed better survival in reuse units after 1991, the more complete M-4 analysis showed no difference in the risk for mortality between reuse and no-reuse units. We conclude that mortality rates in the United States from 1991 to 1995, when adjusted comprehensively for patient and unit characteristics, were not different in units that practiced reuse and those that did not.