School Urinary Screening Program Facilitates Early IgAN Detection, Intervention

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Results confirmed the cost-effectiveness of Japan’s mandated school urinary screening strategy, also pointing to fewer patients progressing to ESKD compared to no screening.

Early IgA nephropathy detection and intervention through urinary screening in school may offer potential cost-effective benefits for reducing the burden of end-stage kidney disease (ESKD) in youth patients, according to findings from a recent economic evaluation and cost-effectiveness analysis of a mandatory screening program in Japan.1

Using a computer-simulated Markov model, investigators assessed the program’s long-term costs and impact on health outcomes compared to no screening, ultimately determining screening was cost-effective and reduced the number of patients with end-stage kidney failure due to IgA nephropathy.1

Given its silent nature, IgA nephropathy often goes undetected for years before patients notice symptoms and seek medical care. Although disease progression is slow, early detection and intervention are necessary to protect the kidneys from further damage by controlling blood pressure, cholesterol, and inflammation.2 Japan has mandated urinary screening in schools since 1973, requiring students to undergo chronic kidney disease screening, although the cost-effectiveness of this approach has not been comprehensively explored.1

“To assess the value of the urinary screening program, a full economic evaluation that includes the effectiveness of CKD early detection and intervention is needed,” wrote Kimiko Honda, MD, MPH, project assistant professor at Keio University Global Research Institute, and colleagues.1

To fill this knowledge gap and evaluate the clinical effectiveness and cost-effectiveness of mandatory school urinary screening in Japanese elementary, junior high, and high schools, investigators used a computer-simulated Markov model to follow a hypothetical cohort of 1,000,000 children 6 years of age. The lifetime follow-up ended at death or age 120 years to allow investigators to assess long-term outcomes, costs, and quality of life measures.1

The entire cohort began in the no IgA nephropathy state at the beginning of the model and was then transitioned to 1 of 5 possible states: no IgA nephropathy, mild IgA nephropathy, severe IgA nephropathy, asymptomatic hematuria, and deceased with initial probabilities. Of note, investigators set the IgA nephropathy incidence as the lowest value of previous reports in Japan, 4.5 cases per 100,000 people. Findings from randomized clinical trials in Japan were used to determine treatment outcomes.1

Investigators calculated the per-patient screening cost by adding the cost of urine containers, carriage, dipstick, and miscellaneous costs from the literature. Costs of detailed examination, treatment, and outpatient follow-up visits were estimated according to the national medical care fee schedule and expert committee and expert opinion recommendations.1

Outcomes were measured using quality-adjusted life-years (QALYs). Costs were calculated in Japanese yen (¥) and 2020 US dollars, where ¥107 = $1. An incremental cost-effectiveness ratio < ¥7,500,000 (US $70,093) per QALY gained was considered cost-effective, a threshold investigators noted is used for pediatric diseases in Japanese official health technology assessments.1

In the base case analysis, the screening program was associated with a ¥9943 (US $93) cost and 39.45039 QALY compared to ¥8338 (US $78) and 39.45001 for the non-screening strategy, respectively. Investigators calculated the incremental cost as ¥1605 (US $15) and the incremental QALY as 0.00038 for the screening versus non-screening strategy. Of note, the corresponding ¥4,186,642 (US $39,127)/QALY incremental cost-effectiveness ratio is less than the selected threshold of ¥7,500,000 (US $70,093).1

The number of patients with ESKD due to IgAN per 1,000,000 patients was greater in the non-screening scenario compared to the screening scenario (60.3 patients vs 31.7 patients). Additionally, investigators pointed out more patients with IgA nephropathy went undetected before 18 years of age per 1,000,000 patients in the non-screening scenario compared to the screening scenario (135.5 vs 27.3 patients).1

In scenario analysis, the screening strategy became dominant by increasing the age at screening initiation to ≥ 15 years (incremental cost, −¥115 [US $1.1]; incremental QALY, 0.00027) and decreasing the screening frequency to < 3 times (incremental cost, −¥75 [US $0.7]; incremental QALY, 0.00025). However, investigators pointed out the number of patients with ESKD or IgA nephropathy undetected before 18 years of age increased in these scenarios. Assuming a disutility of ≥ 0.1 due to false positives in the no IgA nephropathy population, the incremental cost-effectiveness ratio was above the threshold (¥8,304,093 [US $77,608]/QALY).1

Despite the significance of these novel findings, investigators warned the economic evaluations may not be applicable in other countries, especially those without screening programs already in place. They also pointed out varying incidence rates and other considerations in countries outside of Japan that may influence the true cost-effectiveness of a school screening approach. Other limitations were related to a lack of available data and reliance on potentially incorrect assumptions regarding costs of screening and other significant variables.1

“In this economic evaluation with a cost-effectiveness analysis, we found that the Japanese 12-year school urinary screening program was effective, with an associated reduction in the number of patients with ESKD, and cost-effective, focusing on the early detection and treatment of IgAN,” investigators concluded.1


  1. Honda K, Akune Y, Goto R, et al. Cost-Effectiveness of School Urinary Screening for Early Detection of IgA Nephropathy in Japan. Jama Network Open. doi:10.1001/jamanetworkopen.2023.56412
  2. Johns Hopkins Medicine. Immunoglobulin A (IgA) Nephropathy. Conditions and Diseases. Accessed February 16, 2024.