Kidney disease
Can billing codes tell us who has chronic kidney disease?
Open access · cc by · source: Europe PMC
Hospital and doctor billing codes rarely flag kidney disease falsely, but they miss about two out of three older people whose blood tests show reduced kidney function.
Study at a glance
- Design
- Cross-sectional — Retrospective diagnostic-validation study: presence of any of 11 CKD codes in the prior five years (index test) compared against the most recent laboratory eGFR (reference standard) in linked Ontario databases.
- N
- N=123499 · 123,499 adults aged 66 or older in Southwestern Ontario who filled an outpatient prescription between 2007 and 2010 and had a serum creatinine test in the prior year.
- Population
- Older adults (66+) in Southwestern Ontario, Canada, with universal health coverage, excluding those on dialysis or with a kidney transplant.
- Outcome
- Sensitivity, specificity, positive and negative predictive value of the coding algorithm for detecting eGFR below 45 (and below 60 and 30) mL/min per 1.73 m2.
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
About 15% of the cohort had an eGFR below 45, but only 7.7% were flagged by the codes. The algorithm's sensitivity was 32.7% and its specificity 96.9%; positive predictive value was 65.4% and negative predictive value 88.8%. Sensitivity was better for more severe disease (58.8% for eGFR below 30) and was lower in women than men (25.7% vs 43.7%) and in people over 80 than in those aged 66 to 80.
Methodology
Researchers in Ontario linked provincial health databases to laboratory results for 123,499 adults aged 66 and over. Two nephrologists picked 55 possibly relevant diagnosis and billing codes, which were narrowed to a final algorithm of 11 codes; a person counted as 'code positive' if any of these appeared at least once in the previous five years. They compared code status with each person's most recent estimated glomerular filtration rate (eGFR), treating an eGFR below 45 as the reference definition of CKD.
Limitations
CKD was defined from a single eGFR value, whereas clinical diagnosis needs two measurements at least three months apart, and CKD defined by protein in the urine was not captured. The algorithm was built and tested on the same data with no separate validation sample, so its performance may be optimistic and may not transfer to younger people, other provinces or systems without fee-for-service billing. Codes were combined only with a simple 'any code' rule. Because sensitivity differs by sex and age, studies using these codes could produce biased comparisons between groups.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
Codes rarely label someone falsely, but miss about two in three people with reduced kidney function.
Administrative billing codes are specific but insensitive for CKD: in 123,499 Ontario adults aged 66+, codes had 96.9% specificity but only 32.7% sensitivity against eGFR below 45, with lower sensitivity in women (25.7%) than men (43.7%).
Evidence for the claim as stated.
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