Background. Estimated GFR (eGFR) is calculated using serum creatinine (SCr) based equations which have their own limitations. Novel biomarkers like beta trace protein (BTP) are studied for eGFR estimation. The aim of this study is to determine the serum levels of BTP in healthy controls and chronic kidney disease (CKD) cases and to find out the correlation of BTP levels with that of SCr and SCr-based eGFR formulas. Methods. The control group comprised of 20 healthy adults. The cases comprised of 20 patients each in CKD stages 3, 4, and 5, categorized based on eGFR calculated using MDRD formula. Baseline characteristics of the study population were recorded. BTP was measured by ELISA (Enzyme Linked Immunosorbent Assay) method and SCr by modified Jaffe\'s method. The statistical analyses were performed with the SPSS for Windows, version 16.0. Results. The median value of blood urea nitrogen (BUN) in the cases was 26.50 mg/dL (IQR 19.25-37) and for control it was 9.5 mg/dL (IQR 8-12). The median value of SCr in the cases was 2.75 mg/dL (IQR 1.725-4.45) and in the controls, it was 0.7mg/dL (IQR 0.6 -0.8). The median value of BTP in cases was 6389.25 ng/ml (IQR 5610.875-10713.75) and in controls, it was 1089.5 ng/ml (IQR 900.5-1309.75). Conclusion. Serum BTP levels correlated with SCr levels and renal function. We could establish the relationship between the two biomarkers, SCr and BTP, and derive a regression equation.

BACKGROUND: Beta Trace Protein (BTP) is a biomarker for residual kidney function which has been linked to cardiovascular and all-cause mortality in haemodialysis patients. Following renal transplantation, recipients remain at increased risk for cardiovascular events compared with the general population. We aimed to determine the relationship of pre-transplant BTP to major adverse cardiac events (MACE) in patients following kidney transplantation.
METHODS: We included 384 patients with end-stage renal disease who received a kidney transplant. MACE was defined as myocardial infarction (ST-segment elevation or non-ST-segment elevation, stroke or transient ischemic attack), coronary artery disease requiring intervention or bypass or death for cardiovascular reason. The association between pre-transplant serum BTP concentration and post-transplant MACE was evaluated by Kaplan-Meier and Cox regression analyses.
RESULTS: Post-transplant MACE occurred in 70/384 patients. Pre-transplant BTP was significantly higher in patients with post-transplant MACE (14.36 ± 5.73 mg/l vs. 11.26 ± 5.11 mg/l; p < .01). Next to smoking (HR 1.81), age > 56.38 years (HR 1.97) and pre-existing coronary heart disease (HR 8.23), BTP above the cut off value of 12.7 mg/l was confirmed as independent risk factor for MACE (HR 2.02, all p < .05). MACE-free survival inversely correlated with pre-transplant BTP levels.
CONCLUSIONS: Pre-transplant serum BTP concentration may identify renal transplant recipients with higher risk of post-transplant MACE.

OBJECTIVE: Biological variation is defined as the variation in analytical concentration between and within individuals, and being aware of this biological variation is important for understanding disease dynamics. The aim of our study is to calculate the within-subject (CVI) and between-subject (CVG) biological variations of serum creatinine, cystatin C and Beta trace protein (BTP), as well as the reference change value (RCV) and individuality indexes (II), which are used to calculate the glomerular filtration rate while evaluating kidney damage.
METHODS: Blood samples were collected from 22 healthy volunteers for 10 consecutive weeks and stored at -80 °C until the day of analysis. While the analysis for serum creatinine was performed colorimetrically with the kinetic jaffe method, the nephelometric method was employed for cystatin C and BTP measurements. All analyses were carried out in a single session for each test.
RESULTS: Analytical coefficient of variation (CVA) for serum creatinine, cystatin C and beta trace protein was 5.56, 3.48 and 5.37%, respectively. CVI and CVG: for serum creatinine: 3.31, 14.50%, respectively, for cystatin C: 3.15, 12.24%, respectively, for BTP: 9.91, 14.36%, respectively. RCV and II were calculated as 17.94%, 0.23 for serum creatinine, 13.01%, 0.26 for cystatin C, 31.24%, 0.69 for BTP, respectively.
CONCLUSIONS: According to the data obtained in our study, serum creatinine and cystatin C show high individuality, therefore we think that the use of RCV instead of reference ranges would be appropriate. Although II is found to be low for BTP, more studies are needed to support this finding.

Subarachnoid-pleural fistula (SPF) is a rare complication of spine surgery with a transthoracic approach. The outcome of such an injury is affected by not only the pulmonary status due to the pleural effusion but also the neurological one, secondary to the intracranial hypotension. After reviewing the few published cases of SPF, the journey to diagnosis seams heterogenous and the management plan non-uniform. We report the case of a 48-year old women who underwent a right transthoracic discectomy that was complicated by an SPF. The diagnosis, although suspected perioperatively, was established with the gathering of an abundant post-operative pleural effusion, a subdural hematoma on head Computerized Tomography after drainage and Cerebro-Spinal Fluid markers present in the pleural fluid. The defect was effectively corrected with a radiological procedure. We compare our clinical and paraclinical findings and management plans to those reported in the few other published cases of SPF.

Beta Trace Protein (BTP) is a promising marker of glomerular filtration rate (GFR). Equations to estimate GFR using BTP have been proposed. 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 purpose of this study was to assess the impact of cirrhosis on serum BTP concentrations.
BTP, cystatin C (cysC) and creatinine (Cr) were measured in 99 cirrhotic subjects and in 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.
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). 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).
This study suggests that hepatic dysfunction does not influence serum BTP levels and argues against a significant role for the liver in BTP metabolism. Confirmation in a larger group of patients with advanced cirrhosis is required.

BACKGROUND: Beta trace protein (BTP) is a novel renal biomarker that has emerged as potential alternative or addition to serum creatinine (Scr) and serum cystatin C (ScysC). We analyzed BTP\'s diagnostic ability to detect impaired kidney function by rescaling it and we tested whether rescaling BTP allowed us to expand the Full-Age-Spectrum (FAS)-equation to BTP.
METHODS: 566 participants aged ≥70 years with measured glomerular filtration rate (mGFR), Scr, ScysC and BTP from the population-based Berlin Initiative Study (BIS) were considered. We developed a single and combined FAS-equation using rescaled BTP (BTP/0.60) and calculated its sensitivity (S) and specificity (Sp) to identify kidney disease using a fixed (60 mL/min/1.73 m2) and age-dependent threshold for mGFR.
RESULTS: Rescaled BTP shared the same reference interval with rescaled Scr and ScysC and showed acceptable diagnostic performance (S = 73.1%, Sp = 86.5%), comparable to Scr (S = 71.0%, Sp = 90.5%) and ScysC (S = 80.7%, Sp = 92.9%). Rescaled BTP can be used in the FAS-equation with comparable performance as Scr and ScysC, but the Scr/ScysC/BTP-combined FAS-eq. (P10 = 57.8%, P30 = 96.6%) did not outperform the Scr/ScysC-combined FAS-eq. (P10 = 57.1%, P30 = 96.3%).
CONCLUSIONS: Rescaled BTP is a valid alternative to Scr or ScysC to diagnose kidney function. The FAS-concept can be applied to BTP or the combination of BTP, Scr and ScysC.

Residual kidney function (RKF) contributes significant solute clearance in hemodialysis patients. Kidney Diseases Outcomes Quality Initiative (KDOQI) guidelines suggest that hemodialysis dose can be safely reduced in those with residual urea clearance (KRU) of 2 ml/min/1.73 m(2) or more. However, serial measurement of RKF is cumbersome and requires regular interdialytic urine collections. Simpler methods for assessing RKF are needed. β-trace protein (βTP) and β2-microglobulin (β2M) have been proposed as alternative markers of RKF. We derived predictive equations to estimate glomerular filtration rate (GFR) and KRU based on serum βTP and β2M from 191 hemodialysis patients based on standard measurements of KRU and GFR (mean of urea and creatinine clearances) using interdialytic urine collections. These modeled equations were tested in a separate validation cohort of 40 patients. A prediction equation for GFR that includes both βTP and β2M provided a better estimate than either alone and contained the terms 1/βTP, 1/β2M, 1/serum creatinine, and a factor for gender. The equation for KRU contained the terms 1/βTP, 1/β2M, and a factor for ethnicity. Mean bias between predicted and measured GFR was 0.63 ml/min and 0.50 ml/min for KRU. There was substantial agreement between predicted and measured KRU at a cut-off level of 2 ml/min/1.73 m(2). Thus, equations involving βTP and β2M provide reasonable estimates of RKF and could potentially be used to identify those with KRU of 2 ml/min/1.73 m(2) or more to follow the KDOQI incremental hemodialysis algorithm.

Glomerular filtration rate (GFR) is the best indicator of renal function. The gold standard for GFR measurement is inulin clearance. However, its measurement is inconvenient, time-consuming, and costly. Thus, in both scientific studies and routine clinical practice nuclear medicine methods ((99m)Tc-diethylenetriaminepentaacetic acid [(99m)Tc-DTPA] and (51)Cr-ethylenediaminetetraacetic acid [(51)Cr-EDTA]) are preferred, and they correlate strongly with inulin clearance. In addition, cystatin C and β-trace protein have also recently been used for this purpose. In the literature, however, data are limited about the clinical value of cystatin C and β-trace protein in GFR measurement in chronic renal disease (CRD), and the results have been inconclusive. In this study, we aimed to determine the efficiency of cystatin C and β-trace protein in the determination of GFR in CRD patients.
METHODS: Eighty-four patients with CRD were included in the study (59 men and 25 women; age range, 21-88 y; mean age, 61 y). GFR was calculated using the gold-standard (99m)Tc-DTPA 2-sample plasma sampling method (TPSM) and 2 alternative methods: a formula using cystatin C and a formula using β-trace protein. The correlation between TPSM and the cystatin C and β-trace protein methods was assessed, and Bland-Altman analysis was used to graph scatterplots of the differences at a confidence interval of 95% (mean difference ± 1.96 SDs).
RESULTS: GFRs calculated using both alternative methods correlated strongly with those calculated using the gold standard. However, the correlation was stronger for the cystatin C method than for the β-trace protein method, and neither method produced reliably consistent GFRs.
CONCLUSIONS: This study demonstrated that cystatin C and β-trace protein do not reflect GFR with sufficient accuracy.