Trends in nephrology referral patterns for patients with chronic kidney disease: Retrospective cohort study

Abstract

Introduction: Information on early, guideline discordant referrals in nephrology is limited. Our objective was to investigate trends in referral patterns to nephrology for patients with chronic kidney disease (CKD).

Methods: Retrospective cohort study of adults with ≥1 visits to a nephrologist from primary care with ≥1 serum creatinine and/or urine protein measurement <180 days before index nephrology visit, from 2006 and 2019 in Alberta, Canada. Guideline discordant referrals were those that did not meet ≥1 of: Estimated glomerular filtration rate (eGFR) ˂ 30 mL/min/1.73m2, persistent albuminuria (ACR ≥ 300 mg/g, PCR ≥ 500 mg/g, or Udip ≥ 2+), or progressive and persistent decline in eGFR until index nephrology visit (≥ 5 mL/min/1.73m2).

Results: Of 69,372 patients with CKD, 28,518 (41%) were referred in a guideline concordant manner. The overall rate of first outpatient visits to nephrology increased from 2006 to 2019, although guideline discordant referrals showed a greater increase (trend 21.9 per million population/year, 95% confidence interval 4.3, 39.4) versus guideline concordant referrals (trend 12.4 per million population/year, 95% confidence interval 5.7, 19.0). The guideline concordant cohort were more likely to be on renin-angiotensin system blockers or beta blockers (hazard ratio 1.14, 95% confidence interval 1.12, 1.16), and had a higher risk of CKD progression (hazard ratio 1.09, 95% confidence interval 1.06, 1.13), kidney failure (hazard ratio 7.65, 95% confidence interval 6.83, 8.56), cardiovascular event (hazard ratio 1.40, 95% confidence interval 1.35,1.45) and mortality (hazard ratio 1.58, 95% confidence interval 1.52, 1.63).

Conclusions: A significant proportion nephrology referrals from primary care were not consistent with current guideline-recommended criteria for referral. Further work is needed to identify quality improvement initiatives aimed at enhancing referral patterns of patients with CKD.

Fig 1. Flow chart: Cohort selection criteria.

Outpatient eGFR and proteinuria measurements (ACR, PCR, or Udip) in the 6 months preceding the first nephrology visit were used to define guideline concordance of the referral. A visit was guideline concordant if any of the following criteria were satisfied: most recent eGFR < 30 mL/min per 1.73 m2, sustained proteinuria, or progressive decline in eGFR ≥ 5 mL/min per 1.73 m2. Proteinuria was defined as ACR ≥ 300 mg/g, PCR ≥ 500 mg/g, or Udip ≥ 2+, and sustained proteinuria was defined as at least two consecutive proteinuria measurements prior to the date of the nephrology visit. Decline in eGFR ≥ 5 mL/min per 1.73 m2 was defined as a decrease between the first and subsequent eGFR during the 6 months, and progressive decline was defined as at least two consecutive decreases in eGFR by ≥ 5 mL/min per 1.73 m2 prior to the date of nephology visit. Abbreviations: ACR, albumin-creatinine ratio; eGFR, estimated glomerular filtration rate; PCR: protein-creatinine ratio; Udip: urine dipstick.

Fig 2. Annual rate of initial outpatient visits to nephrologists, by guideline concordant/discordant status.

Each year corresponds to the period spanning from April 1 of the previous year to March 31 of that year (e.g., 2006 corresponds to April 1, 2005 to March 31, 2006).

Fig 3. Annual rate of initial outpatient visits to nephrologists, by eGFR (ml/min per 1.73 m2) category.

This cohort includes 61,921 patients who had at least one eGFR measurement in the 6 months prior to the initial nephrology visit. Each year corresponds to the period spanning from April 1 of the previous year to March 31 of that year (e.g., 2006 corresponds to April 1, 2005 to March 31, 2006).

Fig 4. Annual rate of initial outpatient visits to nephrologists, by ACR (mg/g) category.

This cohort includes 31,046 patients who had at least one ACR measurement in the 6 months prior to the initial nephrology visit. Each year corresponds to the period spanning from April 1 of the previous year to March 31 of that year (e.g., 2006 corresponds to April 1, 2005 to March 31, 2006). Conversion factors for units: ACR in mg/g to mg/mmol, x 0.113.