DIFFERENTIATION OF ACUTE FROM CHRONIC RENAL IMPAIRMENT BY DETECTION OF CARBAMYLATED HEMOGLOBIN

Detection of carbamylated haemoglobin, measured as valine hydantoin pe r g haemoglobin (VH/g Hb), may be useful in differentiating between pa tients with acute or chronic renal failure. To assess this test, we me asured carbamylated haemoglobin prospectively in 42 consecutive patien ts referred to the regional renal unit with a serum creatinine in exce ss of 500 mumol/L and a provisional diagnosis of acute renal failure ( ARF). Patients were subsequently classed on clinical criteria as havin g ARF (20) or acute on chronic renal failure (AonCRF, 22). 24 patients with stable chronic renal failure (CRF), matched for degree of renal impairment, were also studied. Standard biochemical tests and haemoglo bin were similar among the three groups. Patients with ARF of 10 or le ss days duration had a lower median (interquartile range [IQR]) carbam ylated haemoglobin concentration than those with a longer duration of ARF (29 [27-35] vs 72 [60-83] mug VH/g Hb; p < 0.01). Carbamylated hae moglobin concentration was lower in the ARF group than in the AonCRF o r CRF groups (42 [31-67], 116 [83-119], and 148 [122-210] mug VH/g Hb, respectively; p < 0.001). All patients with a degree of acute and pot entially, reversible renal failure (ARF and AonCRF) had a carbamylated haemoglobin concentration below 190 mug VH/g Hb (sensitivity 100%, po sitive predictive value 62% for this cut-off). When the ratio of carba mylated haemoglobin to serum creatinine was calculated, to correct for degree of renal failure, a value of less than 0.2 had a 100% sensitiv ity and 80% positive predictive value for dividing patients with poten tially reversible renal failure from those with CRF. Measurement of ca rbamylated haemoglobin was useful in identifying patients with acute a nd potentially reversible forms of renal failure. This test could be o f clinical value in deciding which patients require urgent referral fo r further management and treatment in hospitals without specialist neu phrological care.