One of the main concerns of efficacy of CKD screening programs is the effect of follow-up on decreasing the speed of disease or preventing its inevitable, mainly cardiovascular complications. Our cohort showed a significantly higher survival and a longer time to show a eGFR of less than 15 cc/min in patients who had been under physician supervision compared with those without supervision. Supervised patients also had less need of RRT and less death compared with the control group. Our study confirmed that by using cheap diagnostic tests, characteristics that may predict RRT can be determined and controlled with simple clinical strategies
. It appears that if patients are observed by nephrologists or possibly internists, the rate of decline of kidney function can be slowed and the potential negative consequences of the disease for the individual and the health system can at least be postponed. In our study, we used the maximum level of non-compliance of patients as not referring to a physician for more than 1 year, which was equal to taking less treatment than those who visited their physician regularly, and evaluated its effect on outcome during the cohort. As expected, patient survival was similar at 96% in both groups in the first year. The probability of mortality increases with a decrease in GFR and the accumulated amount of toxic agents over time, which emphasizes the slow nature of the disease and asymptomatic early stages of CKD.
Interestingly, in our study the mortality rate was lower than that in many other studies, including Johnson et al., which found 11.4 deaths/100 person-years and 1.6 progressions to RRT/100 person-years.
 The reason for this difference between studies may be the higher number of old patients in the previous study (56.3% versus 14% older than 75 years). Different methods of patient referral to nephrologists can play a role in difference in outcome. In Iran, a patient who is informed of a kidney problem by the physician can choose to seek advice directly from a nephrologist or go to a family physician or even ignore it. It appears that some patients die before reaching ESRD, the destination of CKD road. In agreement with this possibility is the age distribution of patients who initiate RRT in Iran. According to the ESRD registry, the mean age of men and women who started RRT was 52.5 years and 53.0 years in 2006, respectively, which is lower than many other countries with similar situation
Levin et al. found that in a retrospective cohort of a provincial registry database of patients with an eGFR less than 30 cc/min/1.73 m2 (4231 patients) with access to medical services and a median follow-up of 31 months, there was large heterogeneity of outcome (death or start of RRT). Seventy-six percent of patients with rapid progression (annual eGFR change >5 cc/min/1.73 m2) started RRT but 27% of those with a slower decrease in eGFR started RRT. Interestingly, the authors showed higher systolic blood pressure and phosphorus levels, and lower calcium and albumin levels were associated with a rapid progression and time to RRT by multivariate analysis
. We conclude that managing the above-mentioned variables is important among those who are under medical supervision compared with those without any follow-up.
In a meta-analysis of 13 studies, as part of the process of CKD prognosis collaboration in the KDIGO conference on CKD controversies, a stronger association of lower eGFR with ESRD than mortality was found. The hazard ratios for ESRD in patients with a GFR of 30–44 cc/min/1.73 m2 (2.72; 95% CI: 1.29-3.37) and a GFR of 15–29 cc/min/1.73 m2 (10.21; 95% CI: 8.36-12.46) were significantly higher compared with that for a GFR of 45–74 cc/min/1.73 m2. Similar statistics for mortality in the latter two groups were 1.35 (1.23-1.49) and 2.25 (1.81-2.79), respectively
. An independent association of a lower eGFR with ESRD, all-cause mortality, and the risk of cardiovascular mortality has been confirmed
[14, 15]. However, while the Astor et al. mentioned GFR changes over time, the efficacy and components of treatment, and patients' compliance were not considered for analysis.
The current study found that treated patients with earlier stage of CKD(3a), reached endpoint (32.1%) more than control group(21.4%) , which may raise the issue of generalization, but we speculate that overlapping of the two outcomes of RRT and death is the main reason for this difference. The percentages of those who reached ESRD in stage 3a in both groups of control and treated group were 21.4% versus 21.7% (Table
1). The death rate was higher in the treated group compared with the rate in the control group, which was mainly caused by higher age of patients in the treated group.
The wide standard deviation of the mean follow-up in the groups (33.29±20.50 [7–111] and 36.03±25.24 [6–124] months) was a limitation of the study, which may have had a negative effect on the internal validity of analysis. Another important point in considering the results is the higher portion of CKD stage 4 in the control group. Although this was not statistically significant, it may theoretically have increased the rate of those who reached ESRD. Furthermore, the mean age in the supervised group was significantly higher than that in the control group, which may have increased the occurrence of death.