Background: Late referral to the nephrologist has been mainly examined to assess its causes and effects in patients with chronic renal failure. It has not been analyzed as a phenomenon in itself, to identify its features and allow more effective prevention plans. This study proposes a methodological approach to the study of outpatient referral to the nephrologist (ORN) by defining a number of evaluation tools.
Methods: Patients referred to an outpatient nephrology department represent a cohort of selected subjects on the basis of patient-related factors (clinical, social and cultural) and care-related factors. The incidence and prevalence of kidney disease in this population cannot be considered as a measure of the frequency in the general population. They may represent a first-level approach to the study of ORN by providing an indication of its pattern but not of its actual size in the catchment area. For this purpose we implemented a "referral index", calculated as the percent ratio between the number of affected subjects attending our outpatient department and the number of affected subjects within the whole catchment area.
Results: The number of subjects attending our outpatient department showed a progressive increase, especially among diabetics, in the last 8 years, in concomitance with a collaborative prevention project involving general practitioners. The referral index of the most frequent chronic kidney diseases in 2005 never exceeded 4.9%, accounting for the steady increase in outpatients following our ORN promotion policy. Prevalence on the one hand and referral index on the other provide different types of information about the same subgroup of outpatients: among patients with chronic kidney diseases, prevalence shows a different graduation of ORN than the referral index. Finally, the frequency distribution of chronic kidney disease stages calculated with the referral index moved toward the fourth and fifth stages rather than the second and third stages, as shown by the prevalence.
Conclusions: The incidence and prevalence of renal diseases among outpatients are measures of ORN and they are useful for a qualitative analysis, such as to assess its pattern. The referral index provides a quantitative evaluation of ORN with respect to the general population of the catchment area.