Microalbuminuria in chronic obstructive pulmonary disease.

Background: In this study, the presence of microalbuminuria in patients with chronic obstructive pulmonary disease (COPD) in whom no proteinuria was determined by conventional methods, has been studied taking into account the possible relationship between microalbuminuria and respiratory parameters and their predictive role on mortality.

Methods: Twenty-five cases with COPD who had been hospitalized because of an acute exacerbation and 25 healthy age and sex matched volunteers were included in the study. Microalbuminuria measurement, arterial blood gas analysis, and forced expiratory volume in one second (FEV1), forced vital capacity (FVC) measurements were performed in the COPD group at the beginning of hospitalisation (admission) and after therapy for an average period of 14 +/- 6 days when they were stable at the time of discharge (discharge). Urinary albumin/creatinine (a/c) ratio > or = 2.5 mg/mmol was accepted as microalbuminuria.

Results: Microalbuminuria was detected in 14 (56%) subjects at admission and in 7 (28%) subjects at discharge in the COPD group and in 1 (4%) subject in the control group. There were statistically significant differences among these groups (admission-control p < 0.001, discharge-control p = 0.023, admission-discharge p = 0.016). In COPD group, mean a/c ratio was 3.9 +/- 3.8 at the time of admission, 1.7 +/- 1.9 at discharge and 0.5 +/- 0.5 mg/mmol in the control group. There were statistically significant differences among these groups (admission-control p < 0.001, discharge-control p = 0.029, admission-discharge p = 0.002). In the COPD group there were negative correlation between the microalbuminuria values at admission and arterial pO2 and oxygen saturation (p = 0.031, r = -0.433 and p = 0.002, r = -0.596 respectively). There were no relation between the microalbuminuria values and age, arterial pH, pCO2, FEV1 percent predicted, FVC percent predicted and FEV1/FVC. There were no statistically significant differences between the subjects with or without microalbuminuria according to the median survival time.

Conclusions: In a quite large number of patients with COPD in whom no proteinuria were determined by conventional methods, especially at the time of exacerbation, microalbuminuria could be seen. Microalbuminuria was related with hypoxemia but has no predictive role on mortality.