SP237
SERUM BTP CONCENTRATIONS ARE NOT AFFECTED BY HEPATIC DYSFUNCTION Free

Introduction and Aims: Beta Trace Protein (BTP) is emerging as a promising novel endogenous marker of glomerular filtration rate (GFR). New equations are being developed to convert its serum concentration into an estimate of GFR. Very little is known about BTP’s production and metabolism. It has been hypothesized that the liver metabolizes certain BTP isoforms. As such, hepatic dysfunction may influence serum levels independently of GFR. This would impact on the accuracy and precision of GFR estimates using BTP. The aim of this study was to determine whether patients with hepatic dysfunction have higher than expected serum BTP concentrations due to reduced hepatic BTP clearance.

Methods: BTP, cystatin C (cysC) and creatinine (Cr) were measured in 99 cirrhotic subjects and in age, gender and diabetes status matched controls. BTP/cysC and Cr/cysC ratios were compared between cases and controls. This was repeated after stratification by Child Pugh category. Comparisons of ratios between Child Pugh category A and combined B and C case subjects were also performed. The BTP/cysC ratio was chosen in lieu of the BTP/Cr ratio due to the well-recognized inaccuracy of Cr as a marker of GFR in the setting of hepatic dysfunction. Prior studies have shown a strong inverse relationship between inulin GFR and cysC in cirrhotic patients and a lack of impact of cirrhosis on serum cysC levels, suggesting that cysC is an acceptable surrogate for measured GFR.

Results: There were no differences in BTP/cysC ratios between cases and controls for the entire cohort (0.80 vs 0.79) or for any of the Child Pugh categories (p > 0.10 for all). There were significant differences between cases (1.09) and controls (0.73) for the BTP/Cr ratios (p<0.001). The BTP/Cr ratio was higher in those with more advanced cirrhosis as compared to those with less severe cirrhosis (1.20 vs 1.03, p<0.01). There were no differences in BTP/cysC ratios between those with less severe and more advanced cirrhosis (p=0.25).

Conclusions: This study suggests that, unlike serum Cr, serum BTP concentrations are independent of hepatic dysfunction. BTP might therefore serve as a particularly useful marker of GFR, either alone or in combination with cysC, in patients with cirrhosis. Further study of other non-GFR dependent factors which may influence serum BTP concentration levels is required to allow for a better understanding of how to best incorporate BTP into clinical care.