Tubular secretion of creatinine in autosomal dominant polycystic kidney disease: consequences for cross-sectional and longitudinal performance of kidney function estimating equations.
BACKGROUND
Autosomal dominant polycystic kidney disease (ADPKD) is characterized by renal tubular cell proliferation and dedifferentiation, which may influence tubular secretion of creatinine (CCr[TS]).


STUDY DESIGN
Diagnostic test study.


SETTING & PARTICIPANTS
We therefore investigated CCr(TS) in patients with ADPKD and controls and studied consequences for the performance of glomerular filtration rate (GFR) estimating equations.


INDEX & REFERENCE TESTS
In patients with ADPKD and healthy controls, we measured GFR as (125)I-iothalamate clearance while simultaneously determining creatinine clearance.


OTHER MEASUREMENTS
24-hour urinary albumin excretion.


RESULTS
In 121 patients with ADPKD (56% men; mean age, 40 ± 11 [SD] years) and 215 controls (48% men; mean age, 53 ± 10 years), measured GFR (mGFR) was 78 ± 30 and 98 ± 17 mL/min/1.73 m(2), respectively, and CCr(TS) was 15.9 ± 10.8 and 10.9 ± 10.6 mL/min/1.73 m(2), respectively (P < 0.001). The higher CCr(TS) in patients with ADPKD remained significant after adjustment for covariates and appeared to be dependent on mGFR. Correlation and accuracy between mGFR and CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) estimated GFR (eGFR) were 0.95 and 99%, respectively; between mGFR and MDRD (Modification of Diet in Renal Disease) Study eGFR, they were 0.93 and 97%, respectively. Values for bias, precision, and accuracy were similar or slightly better than in controls. In addition, change in mGFR during 3 years of follow-up in 45 patients with ADPKD correlated well with change in eGFR.


LIMITATIONS
Cross-sectional, single center.


CONCLUSIONS
CCr(TS) in patients with ADPKD is higher than that in controls, but this effect is limited and observed at only high-normal mGFR. Consequently, the CKD-EPI and MDRD Study equations perform relatively well in estimating GFR and change in GFR in patients with ADPKD.
['Spithoven|Edwin M|EM|', 'Meijer|Esther|E|', 'Boertien|Wendy E|WE|', 'Sinkeler|Steef J|SJ|', 'Tent|Hilde|H|', 'de Jong|Paul E|PE|', 'Navis|Gerjan|G|', 'Gansevoort|Ron T|RT|']
D000328:Adult D003404:Creatinine D003430:Cross-Sectional Studies D005260:Female D005500:Follow-Up Studies D005919:Glomerular Filtration Rate D006801:Humans D007677:Kidney Function Tests D007684:Kidney Tubules D008137:Longitudinal Studies D008297:Male D008875:Middle Aged D016891:Polycystic Kidney, Autosomal Dominant
tubular secretion of creatinine creatinine Autosomal dominant polycystic kidney disease (ADPKD) measured GFR estimated glomerular filtration rate (eGFR)