Maurizio Nordio

Interaction between parathyroid hormone and the Charlson comorbidity index on survival of incident haemodialysis patients

BACKGROUND Haemodialysis patients are ageing and have with a high rate of comorbidities. The impact of this novel clinical setting on intact parathyroid hormone (iPTH) is not well established. METHODS For this observational, prospective multicentre cohort study, incident haemodialysis patients were recruited in 40 Italian centres and followed up for a mean period of 18 +/- 6.7 months. Clinical characteristics and biochemistry were recorded at baseline. Comorbid conditions were scored by the Charlson comorbidity index (CCI). RESULTS Data of 411 patients (mean age: 66.5 +/- 14.8 years; 17.3% >80 years old) were recorded. The mean CCI was 4.17 +/- 2.8. In patients with CCI >0, an inverse correlation was observed between CCI (excluding age) and iPTH (P = 0.00002). Independently of CCI, patients with iPTH <150 pg/ml had 76% as high as the risk of all-cause mortality. After multivariable adjustment, the combination of the first tertile of iPTH with second and third tertiles of CCI was significantly associated with all-cause mortality (RR = 3.83, P = 0.02; RR = 3.79, P = 0.01, respectively). CONCLUSIONS Incident haemodialysis patients suffer from a high rate of clinical complications. In these patients, low iPTH and high CCI are often associated and very likely responsible for an adverse outcome.

Comparison between creatinine-based equations for estimating total creatinine clearance in peritoneal dialysis: a multicentre study

BACKGROUND It is crucial to assess the adequacy of peritoneal dialysis (PD) because of its influence on patient outcome. Collecting dialysate and urine for 24 h can be rather troublesome, so a simple and inexpensive alternative method for rapidly evaluating adequacy in PD would be very useful. Our study aimed to assess the performance of 12 different creatinine (Cr)-based equations commonly used to estimate GFR in predicting total Cr clearance (totCrCL) in PD. METHODS Four Italian dialysis centres enrolled 355 PD patients with 2916 fluid collections. To rank the equations, their accuracy (median absolute percentage error, MAPE), precision (root mean square error, RMSE), agreement (k statistics), sensitivity and specificity (area under ROC curves, AUC, where x = 1 - specificity and y = sensitivity) were calculated with reference to the measured totCrCL. RESULTS The Gates, Virga and 4-MDRD equations showed the best global performance as concerns accuracy (MAPE = 14.1, 16.3, 15.9% respectively), precision (RMSE = 13.2, 13.3, 13.4), agreement (k = 0.425, 0.440, 0.375), sensitivity and specificity (AUC = 0.825, 0.826, 0.820), while the Cockcroft-Gault formula revealed a rather poor reliability. CONCLUSIONS Fluid collection remains the gold standard for assessing PD adequacy. Our study ascertained how 12 Cr-based equations performed in estimating totCrCL in PD patients with a view to enabling the most accurate and precise among them to be chosen for use in approximately assessing totCrCL.

Mortality in the Veneto population on renal replacement therapy.

This section reports survival rates for patients on renal replacement therapy (RRT). The data obtained from the Veneto Dialysis and Transplantation Registry (VDTR) cover the whole population in the region. Patients on RRT alive on 31 December of each year were assumed to be at risk of dying in the following year. Furthermore, time-to-event analysis was used to describe the complete history of patients from when they started RRT until they died, including transitions between the 3 main treatment modalities - hemodialysis (HD), peritoneal dialysis (PD) and renal transplantation. The cohort of patients starting RRT from 1998 to 2010 was followed up until 31 December 2010. Survival rates from the first treatment to death were calculated according to the life table method. Relative survival and excess mortality rates were estimated according to the Ederer II method. A multistate model was used to describe changes in a patients condition (changes of treatment, or death) over time. Among prevalent patients on RRT, the annual risk of death was 10.65% in 2008, 9.35% in 2009 and 8.86% in 2010. The overall mortality rate was 12.5 per 100 patient-years (95% confidence interval [95% CI], 12.1-13.0). The 5-year relative survival was 59% (95% CI, 57%-60%), and at 10 years relative survival was 41% (95% CI, 39%-43%); the estimated excess mortality rate was very high at the start of RRT (18 per 100 patient-years) but gradually decreased after the second year. On multivariate analysis, excess mortality was associated with age and primary renal diseases. Less than 10% of patients starting on PD shifted to HD in the first year of RRT, and a considerable proportion received a transplant, amounting to 6% in the first year, and thereafter increasing steadily: at the end of the fifth year, 34% of patients starting RRT on PD had received a transplant. HD patients behaved differently: any shift to PD was negligible, and the patients receiving a transplant amounted to only 2% in the first year and about 16% by the end of the fifth year. Cumulative mortality among HD patients was particularly high (already 18% at 1 year, and 70% at 10 years) by comparison with those on PD (8% at 1 year, 54% at 10 years). Although mortality on RRT is not particularly high in Veneto by comparison with countries other than Italy, this result is mainly due to an increasing number of patients receiving transplants, which makes them a favorably selected population. The mortality rate was high among those on HD, particularly in the first year. Our population on RRT is rather heterogeneous, and a description of the outcomes based only on the whole population may be misleading.

Performance of an easy to use prediction model for renal patient survival: an external validation study using data from the ERA-EDTA Registry

Background An easy-to-use prediction model for long-term renal patient survival based on only four predictors [age, primary renal disease, sex and therapy at 90 days after the start of renal replacement therapy (RRT)] has been developed in The Netherlands. To assess the usability of this model for use in Europe, we externally validated the model in 10 European countries. Methods Data from the European Renal Association-European Dialysis and Transplant Association (ERA-EDTA) Registry were used. Ten countries that reported individual patient data to the registry on patients starting RRT in the period 1995-2005 were included. Patients <16  years of age and/or with missing predictor variable data were excluded. The external validation of the prediction model was evaluated for the 10- (primary endpoint), 5- and 3-year survival predictions by assessing the calibration and discrimination outcomes. Results We used a data set of 136 304 patients from 10 countries. The calibration in the large and calibration plots for 10 deciles of predicted survival probabilities showed average differences of 1.5, 3.2 and 3.4% in observed versus predicted 10-, 5- and 3-year survival, with some small variation on the country level. The concordance index, indicating the discriminatory power of the model, was 0.71 in the complete ERA-EDTA Registry cohort and varied according to country level between 0.70 and 0.75. Conclusions A prediction model for long-term renal patient survival developed in a single country, based on only four easily available variables, has a comparably adequate performance in a wide range of other European countries.