1 Hospital Universitario Dr Peset, Valencia 2 Hospital Arnau de Vilanova, Lleida 3 Hospital de la Princesa, Madrid 4 Hospital Virgen Macarena, Sevilla 5 Hospital Ntra. Sra. de Alarcos, Ciudad Real, Spain
Sir,
We have read with great interest the paper published recently by Jungers et al. [1]. This study provides additional evidence that longer duration of regular nephrological care in the pre-dialysis period is associated with a better long-term survival on dialysis. The authors comment about the lack of studies that analyse such a hypothesis. Related to this point, we report our experience in Spain [2], which offers results very similar to those obtained by Jungers et al. [1]. Our results, however, reinforce the fact that pre-dialysis nephrological care (PNC) indeed improves the outcome of dialysis patients. Nevertheless, we have found that the better outcome is achieved mainly in patients with a duration of PNC of longer than 36 months.
This retrospective analysis concerns a total of 362 patients (227 male and 135 female) from five hospitals of the Spanish National Health System who initiated chronic renal replacement therapy (RRT) during 1996 and 1997. Patients who initiated chronic dialysis after acute renal failure were excluded. The demographic characteristics, patients' conditions at the time of initiating dialysis and outcome (hospitalizations during the first 6 months after RRT and mortality) in relation to the duration of PNC duration were analysed. This duration was quantified as the time interval between the start of nephrological regular care and the day of initiation of dialysis. Patients were classified according to duration of PNC in <6 months, 636 months, and >36 months. Patients who initiated RRT with a vascular or peritoneal access ready to use were considered as planned dialysis, if not they were classified as unplanned dialysis. Patients were grouped according to co-morbid status into high, medium, or low risk using stratification as recommended by Wright and Khan [3].
The mean age of the 362 patients at the start of dialysis was 62.8±16 years (range 1891) and the mean and median follow up were 39±16 months (range 160) and 43.5 months, respectively. One hundred and three patients (28.5%) were diabetics, with diabetic nephropathy as aetiology of end-stage renal disease (ESRD) diagnosed in 78 of them (21.5%). Other aetiologies were: glomerular in 23.5%, interstitial diseases in 17.7%, vascular diseases in 19.3%, polycystic kidney disease in 5.8%, and other diseases in 21.5% of the patients. Previous cardiovascular disease (myocardial infarction, coronary artery revascularization, cerebral infarction, congestive heart failure, or peripheral arteriopathy) [1] at the start of dialysis was detected in 160 patients (44.2%). The duration of PNC was <6 months in 73 patients (20.2%), 636 months in 185 patients (51.1%), and >36 months in 104 patients (28.7%). Two hundred and seventy eight patients (76.8%) were referred to a nephrologist at least 6 months prior to the first dialysis. One hundred and eighty-six patients (51.4%) started RRT as planned dialysis, whereas 176 (48.6%) as unplanned dialysis (P<0.001).
Based on the PNC duration stratification, ANOVA analysis at initiation of dialysis showed significant differences in sex (P=0.007), diabetes (P=0.012), co-morbidity risk groups (P=0.037), reason for initiating dialysis (P<0.001), initiation of RRT as planned dialysis (P<0.001), diastolic blood pressure (P=0.01), duration of hospitalization both at initiation of RRT and within the first 6 months (P<0.001), haemoglobin level (P=0.001), increased blood transfusion requirements (P<0.001), necessity of a central venous catheter (P<0.001), and body weight (P=0.037). On the other hand, with the same analysis, no significant differences at initiation of dialysis in age, aetiology of ESRD, dialysis modality, family support, and previous cardiovascular disease (P=n.s.), as well as in Cockcroft creatinine clearance, and levels of albumin, potassium, calcium, phosphorus, and bicarbonate were found.
Survival rates at 12, 24, and 36 months were 82, 73, and 68% in the group with <6 months PNC, 85, 79, and 69% in the group with 636 months PNC, and 91, 85, and 82% in the patients with a PNC of >36 months. KaplanMeier analysis showed higher survival in the group with a PNC >36 months than in patients with 636 months and <6 months (P=0.01, log rank test).
Multivariate analysis using Cox proportional hazard found independent risk factors at initiation of dialysis for death such as age (P=0.001; RR, 1.06; CI 95%, 1.031.08), prior cardiovascular disease (P=0.01; RR, 1.90; CI 95%, 1.103.28), PNC duration <6 months (P=0.0011; RR, 2.95; CI 95%, 1.535.65), PNC duration 636 months (P=0.015; RR, 2.71; CI 95%, 1.206.11) (reference: PNC duration >36 months), serum albumin (P=0.003; RR, 1.96; CI 95%, 1.352.76), diastolic blood pressure (P=0.05; RR, 1.01; CI 95%, 0.991.040), and Cockcroft creatinine clearance (P=0.06; RR, 1.08; CI 95%, 0.991.18).
Late referral to the nephrologist is associated with poor pre-ESRD care [35], but early referral does not always guarantee optimal pre-ESRD care, at least in some patients, especially cardiovascular high-risk patients. According to the type of renal disease it may take several years to progress to ESRD. In many cases even 6 months of nephrological care may not be enough to guarantee optimal management of chronic renal failure. The most striking finding in our study is that longer duration of PNC is associated with better overall clinical conditions at the initiation of dialysis and less morbidity and mortality in dialysis patients. So, pre-ESRD follow up should be initiated as early as possible once advanced chronic renal failure is detected.
For all these reasons, nephrologists must do their best for general practitioners and non-nephrological specialists to refer patients at the right time and emphasize the importance of early and regular nephrological follow up, close monitoring, and the development of educational programmes for pre-ESRD patients.
Acknowledgments
We would like to thank Dr Norbert Lameire for his expert advice and assistance.
Notes
References