Abstract
Background and Aims:
Chronic kidney disease (CKD) is a public health burden affecting >10% of the population worldwide. Population-based studies are essential to assess CKD prevalence and its determinants. However, questionnaires to survey CKD and other kidney diseases in the general population are scarce. We developed a novel questionnaire to identify several types of kidney disease in the general population and implemented it in a large central-European population study.
We integrated questionnaire responses with standard renal biochemical measurements to estimate CKD prevalence in the Val Venosta/Vinschgau district. We aimed to assess the degree of CKD underdiagnosis and to describe the kidney health status of study participants.
Method:
Within the Cooperative Health Research In South Tyrol (CHRIS) study, we conducted a cross-sectional assessment of kidney health on 11684 adults (mean age 45 years; females 53.8%) with interviewer-administered kidney questionnaire and measured fasting serum creatinine and albuminuria.
The questionnaire covered retrospectively various kidney diseases, including reduced renal function and renal surgeries (Figure 1). Questions asked if a doctor had ever diagnosed the specific condition and the age at diagnosis. We defined CKD based on combinations of self-reported diagnosis of reduced kidney function (Q6), CKD-EPI 2021 estimated glomerular filtration rate (eGFR) levels, and microalbuminuria (Table 1). Prevalence was estimated via the Clopper-Pearson method and adjusted to the general target population via relative sampling weights. Using factor analysis we explored the underlying correlation structures within and between questionnaire items and laboratory markers.
Results:
Participants had median eGFR and urinary albumin-to-creatinine ratio (UACR) of 98.4 ml/min/1.73m2 (IQR: 87.8-108.8) and 5.7 mg/g (IQR: 3.8-10.0), respectively. Overall, 744 reported only one and 179 reported at least two types of kidney diseases (Figure 1). Glomerulonephritis (n=359; 3.14%), kidney stones (n=311; 2.93%) and other kidney diseases (n=200; 1.91%) were the most frequent types. Males reported kidney stones (M: 3.2%; F: 2.2%; p-value=0.0013) and renal surgeries (M: 0.9%; F: 0.5%; p-value=0.0116) more frequently than females. Females reported a higher proportion of glomerulonephritis (M: 0.6%; F: 5.2%; p-value<0.0001). The population-weighted CKD prevalence varied between 0.71% to 9.29% depending on the definition (Table 1), with a KDIGO estimate of 8.79% (95%CI 8.28%-9.31%). Questionnaire items showed low sensitivity and high specificity to identify low eGFR or high UACR levels. Factor analysis revealed two clearly separated latent factors: one representing “reduced renal function”, which included eGFR, UACR, and the question Q6 on reduced kidney function; and one representing “all other kidney diseases”.
Conclusion:
In the Val Venosta/Vinschgau district, CKD prevalence is aligned to Western-European countries. In general population studies, questionnaire-based CKD assessment may severely underestimate CKD prevalence as compared to eGFR- and UACR-based estimates. Our analysis highlights that the large majority of individuals with CKD according to KDIGO guidelines were unaware of the disease. On the other hand, the questionnaire has allowed identifying several specific kidney diseases that usually go undetected in population studies. The limited discriminant ability of questionnaire items and the identifiable correlation structure support the use of the survey questionnaire as an integrative tool to study the kidney health status in general population.
Figure:
Figure 1: Summary of the responses to the kidney questionnaire. Combinations reported by ≤2 participants were excluded.
Table 1: Comparison of population-weighted CKD prevalence
Definition
Prevalence
95%CI-Lower
95%CI-Upper
(1) Questionnaire self-rep. reduced kidney function (Q6)
0.71%
0.56%
0.88%
(2) CKD G3 to G5 (eGFR < 60 ml/min/1.73m2)
2.56%
2.28%
2.87%
(3) Microalbuminuria (UACR > 30 mg/g)
7.07%
6.62%
7.55%
(4) KDIGO: "Moderately increased" to "Very high" risk – (2) or (3)
8.79%
8.28%
9.31%
Any CKD definition
9.29%
8.77%
9.84%