Increased urinary haemoglobin in diabetics with microalbuminuria--measured by an ELISA

A solid-phase sandwich enzyme immunoassay for the determination of urinary haemoglobin is described. A screening study was performed to establish whether occult haematuria/haemoglobinuria is present in diabetic patients with elevated urinary albumin excretion. Non-insulin-dependent diabetic patients (145) aged 66.5 years +/- 5.6 with a known duration of diabetes of 10.4 years +/- 6.8 were studied. They delivered a first morning urine sample at consecutive outpatient visits. Erythrocytes were lysed by freezing of the urine samples. The patients were categorized into three groups according to urinary albumin concentration (UAC) as measured by radio-immunoassay. Forty-five patients with microalbuminuria i.e. UAC greater than 20- less than or equal to 200 micrograms/ml had an elevated urinary haemoglobin concentration (UHC) of 38.5 micrograms/l compared to 90 patients with normal UAC and a UHC of 7.7 micrograms/l, p less than 10(-4). A further increase was seen in 10 proteinuric patients, UHC 161.8 micrograms/l, p less than 0.05. The urinary concentration of albumin and haemoglobin were significantly correlated, r = 0.49, p less than 10(-8). In 32 insulin-dependent diabetics the findings were similar. There was no correlation between either age or known duration and the haemoglobin concentration. In 42 normal subjects, the UHC was 3.6 micrograms/lx/divided by 6.1. Haematuria has formerly been described in patients with diabetic nephropathy alone. The present findings suggest that occult haematuria/haemoglobinuria is already present in patients with microalbuminuria.