Comparison of urinary albumin and urinary total protein as predictors of patient outcomes in CKD.
BACKGROUND
Proteinuria is common and is associated with adverse patient outcomes. The optimal test of proteinuria to identify those at risk is uncertain. This study assessed albuminuria and total proteinuria as predictors of 3 patient outcomes: all-cause mortality, start of renal replacement therapy (RRT), and doubling of serum creatinine level.


METHODS
Retrospective longitudinal cohort study.


METHODS
Nephrology clinic of a city hospital in Scotland; 5,586 patients with chronic kidney disease (CKD) and proteinuria measured in random urine samples (n = 3,378) or timed urine collections (n = 1,808).


METHODS
Baseline measurements of albumin-creatinine ratio (ACR), total protein-creatinine ratio (PCR), 24-hour albuminuria, and total proteinuria.


RESULTS
All-cause mortality, start of RRT, and doubling of serum creatinine level were assessed using receiver operating characteristic curves and Cox proportional hazards models.


METHODS
Blood pressure, serum creatinine level, ACR, PCR, date of death, date of starting RRT.


RESULTS
Patients were followed up for a median of 3.5 (25th-75th percentile, 2.1-6.0) years. For all outcomes, adjusted HRs were similar for PCR and ACR (derived from random urine samples and timed collections): death, 1.41 (95% CI, 1.31-1.53) vs 1.38 (95% CI, 1.28-1.50); RRT, 1.96 (95% CI, 1.76-2.18) vs 2.33 (95% CI, 2.06-3.01); and doubling of serum creatinine level, 2.03 (95% CI, 1.87-2.19) vs 1.92 (95% CI, 1.78-2.08). Receiver operating characteristic curves showed almost identical performance for ACR and PCR for the 3 outcome measures. Adjusted HRs for ACR and PCR were similar when derived from random urine samples or timed collections and compared with 24-hour total protein and albumin excretion for each outcome measure.


CONCLUSIONS
This is a retrospective study.


CONCLUSIONS
Total proteinuria and albuminuria perform equally as predictors of renal outcomes and mortality in patients with CKD. ACR and PCR were as effective as 24-hour urine samples at predicting outcomes and are more convenient for patients, clinicians, and laboratories. Both ACR and PCR stratify risk in patients with CKD.
Crosshouse Hospital, Kilmarnock, UK. shona.methven@nhs.net
Shona
S
Methven
Mark S
MS
MacGregor
Jamie P
JP
Traynor
Mario
M
Hair
Denis St J
DS
O'Reilly
Christopher J
CJ
Deighan
D000419:Albuminuria / Q000652:urine*; D003404:Creatinine / Q000652:urine; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011507:Proteinuria / Q000652:urine*; D012372:ROC Curve; D051436:Renal Insufficiency, Chronic / Q000175:diagnosis / Q000401:mortality* / Q000628:therapy / Q000652:urine; D017582:Renal Replacement Therapy; D016019:Survival Analysis
D003404:Creatinine