Use of APACHE-II as a prognostic score index for non-ICU patients with acute renal failure (ARF)

The APACHE-II score has been used as an index of severity of illness for non-ICU patients with ARF in some studies. We sought to investigate the differences between ICU and non-ICU patients, and to determine whether APACHE-II can or cannot be used as a prognostic score index for non-ICU patients and to compare it with the ATN-ISS. To this end, we collected data from 205 ARF patients at the Hospital São Paulo - a university based, not-for-profit, tertiary hospital - between February 1997 and November 1997. APACHE-II scores were calculated at the time of hospital admission (AP-1) and time of referral to the nephrologist (AP-2). The ATN-ISS score was also obtained at the time of referral to the nephrologist. The period prevalence of ARF during the study was 1% (205/19524 admissions). There were 98 males and 107 females, with a mean age of 52 ± 18 years, and 70 patients (34%) required dialysis. Sixty-eight patients (33%) were admitted to the ICUs and 137 (67%) were treated in the wards or at the emergency ward. The overall mortality rate was 46%. In multivariate analysis, no differences were found between non-ICU and ICU patients for age, gender or oliguria. However, non-ICU patients had lower frequency of shock (25% versus 57%; P = 0.007) and mechanical ventilation (25% versus 60%; P = 0.007), a lower ATN-ISS (0.41 versus 0.78; P < 0.001), a lower AP1 (16.5 versus 19; P = 0.02) and a lower risk of death as calculated using the AP1 (23% versus 50%; P < 0.001). Non-ICU patients also needed dialysis less often (32% versus 38%; P = 0.003) and had a lower mortality rate (31% versus 78%; P < 0.001), compared to ICU patients. The observed/expected mortality ratio was similar in both groups (1.34 for non-ICU versus 1.56 for ICU patients). The area under the receiver operator curve was similar between ICU and non-ICU patients for AP1 (0.63 versus 0.66; P = 0.78), AP2 (0.71 versus 0.80; P = 0.21) and for the ATN-ISS (0.95 versus 0.96; P = 0.80), suggesting that the APACHE-II collected at hospital admission or at the time of referral to the nephrologist and ATN-ISS can be used as severity of illness scores for non-ICU patients.