Chronic kidney disease (CKD) constitutes a global public health problem with increasing prevalences driven by diabetes and hypertension.1 The REVEAL-CKD study estimated that up to 95% of European patients with stage 3 CKD remain undiagnosed,2 highlighting the need for early detection strategies. However, most population-based studies rely on single measurements, which may overestimate the true prevalence.
Objectives and methodsDuring November 2023, we conducted an opportunistic CKD screening in adults attending the Jerez Sur Primary Care Center for routine laboratory tests. The study included two phases: initial screening (phase 1) based on estimated glomerular filtration rate (CKD-EPI), urine albumin-to-creatinine ratio (UACR), and urinary sediment, followed by diagnostic confirmation at three months (phase 2) according to KDIGO criteria.3
ResultsA total of 422 patients participated (60.4% women, mean age 54.6 ± 16.6 years) with a high burden of cardiovascular risk factors: hypertension (46.4%), diabetes (22.3%), and dyslipidemia (41.5%).
Initial screening detected possible CKD in 105 patients (25%), meeting criteria for eGFR < 60 mL/min/1.73 m2, UACR ≥ 30 mg/g, hematuria ≥ 25 red blood cells/µL, or leukocyturia ≥ 15 white blood cells/µL.
After diagnostic confirmation at three months, CKD was confirmed in only 38 patients (9% of the total sample); in seven additional patients, CKD confirmation was made by their own physicians (1.65%). Diagnostic confirmation ruled out CKD in nearly two-thirds of those initially classified as at risk (Table 1).Multivariate analysis identified diabetes (OR: 1.90; 95% CI: 1.11–3.27) and hypertension (OR: 2.35; 95% CI: 1.42–3.89) as significant risk factors. The prevalence of classic comorbidities and age were markedly higher in the subgroup with confirmed CKD, which also exhibited a nearly two-fold SCORE24 risk compared to the group without CKD (20.63 ± 17.11 vs. 8.81 ± 9.17 points; p < 0.001).
Comparison between initial screening and diagnostic confirmation.
| Parameter | Phase 1 (screening) | Phase 2 (confirmation) |
|---|---|---|
| Mean age (years, SD) | 61.0 (16.1) | 66.0 (14.5) |
| Hypertension (%) | 67.6 | 73.7 |
| Diabetes (%) | 34.3 | 50.0 |
| Dyslipidemia (%) | 53.3 | 65.8 |
| Cardiovascular events (%) | 9.5 | 18.4 |
| eGFR < 60 mL/min/1.73 m², n (%) | 23 (21.9%) | 17 (44.7%) |
| UACR ≥ 30 mg/g, n (%) | 26 (24.8%) | 14 (36.8%) |
| Hematuria ≥ 25/µL, n (%) | 22 (21.0%) | 7 (18.4%) |
| Leukocyturia ≥ 15/µL, n (%) | 64 (61.0%) | 21 (55.3%) |
| Possible CKD, n (%) | 105 (24.9%) | 38 (9.0%) |
Our results demonstrate that screening based on a single measurement significantly overestimates CKD prevalence, consistent with previous Spanish studies reporting prevalences of 14–16% based on single measurements.5,6 Diagnostic confirmation is crucial to differentiate between transient abnormalities and persistent kidney damage.This discrepancy has important clinical and public health implications. Without diagnostic confirmation, we would have overestimated the prevalence by 134% (25% vs. 10.65%), which would have resulted in unnecessary medicalization and anxiety in patients with transient abnormalities.
The higher frequency of CKD in women > 55 years (a distinctive finding of our study) warrants further investigation, as it contrasts with the literature describing a higher prevalence in men.7
Implications for clinical practiceOpportunistic screening is feasible in primary care, especially when targeted at high-risk groups (diabetes, hypertension, dyslipidemia).
Screening based on a single measurement markedly overestimates CKD prevalence. Applying diagnostic confirmation at three months as recommended by the KDIGO guidelines is essential to avoid overdiagnosis and accurately assess the true impact of CKD, particularly in subjects with cardiovascular risk factors.
In patients with confirmed CKD, cardiovascular risk is doubled, reinforcing its role as a global risk marker to be systematically included in cardiovascular risk stratification.8Implementing automated alerts in laboratory tests could optimize detection and follow-up.9
Limitations. Follow-up losses (29.5%) and the single-center design limit the generalizability of results, requiring validation in multicenter studies.
ConclusionsOpportunistic CKD screening in primary care is effective when targeted at at-risk populations, but diagnostic confirmation is essential to avoid overdiagnosis and accurately estimate the true prevalence. Confirmed CKD is associated with significantly elevated cardiovascular risk, reinforcing the need for its inclusion in risk stratification algorithms. These findings underscore the importance of following KDIGO recommendations requiring two measurements for the definitive diagnosis of CKD.10
FundingNo funding was received for the development of the content of this letter.
The authors declare that they have no conflicts of interest.
