Nephrology

Acute Interstitial Nephritis Risk calculator

Enter the published formula inputs below to calculate and interpret this score.

Clinical inputs

Serum creatinine before biopsy

mg/dL

Allowed range: 0.2–20 mg/dL

The natural log uses mg/dL. A value entered in µmol/L is divided by 88.4.

Blood urea nitrogen

mg/dL

Allowed range: 1–200 mg/dL

Enter BUN in mg/dL. Urea in mmol/L is multiplied by 2.801. The model uses the ratio of this BUN to creatinine in mg/dL.

Urine dipstick specific gravity

Allowed range: 1.001–1.04

Dipstick specific gravity, such as 1.010. Each 0.001 above 1.000 lowers the logit.

Urine dipstick protein

0 or 1+ adds 0.9360127 to the logit. 2+ or higher adds nothing.

Result

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Primary source

Moledina DG et al. Development and external validation of a diagnostic model for biopsy-proven acute interstitial nephritis using electronic health record data. Nephrol Dial Transplant. DOI: 10.1093/ndt/gfab346. PMID: 34865148. Table 4 odds ratios and the printed intercept 0.770398. Development-cohort weights, read from the later validation supplement that reprints them: logit = 0.8367518 × ln(creatinine in mg/dL) − 0.9181938 × ln(BUN/creatinine) − 0.0501203 × (specific gravity − 1) × 1000 + 0.9360127 if dipstick protein is 0 or 1+, otherwise 0, + 0.770398. Probability = exp(logit) / (1 + exp(logit)). Urea in mmol/L is multiplied by 2.801 to reach BUN in mg/dL. Table 5 in the external biopsy cohort: at 5% sensitivity 0.94 and specificity 0.32; at 10% sensitivity 0.71 and specificity 0.63; at 25% sensitivity 0.27 and specificity 0.94. This is the development intercept, not the later prevalence shift of ln(local prevalence / 0.23). (2022)

Scope: Adults already selected for a kidney biopsy. The model was fit in that setting and was not studied in people who did not undergo biopsy.

Last reviewed 2026-10-17

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Professional use only

For qualified clinicians. Independently verify inputs, calculations, source guidance, and applicability before any clinical action. This calculator does not replace clinical judgment.

Source: Moledina DG et al. Development and external validation of a diagnostic model for biopsy-proven acute interstitial nephritis using electronic health record data. Nephrol Dial Transplant. DOI: 10.1093/ndt/gfab346. PMID: 34865148. Table 4 odds ratios and the printed intercept 0.770398. Development-cohort weights, read from the later validation supplement that reprints them: logit = 0.8367518 × ln(creatinine in mg/dL) − 0.9181938 × ln(BUN/creatinine) − 0.0501203 × (specific gravity − 1) × 1000 + 0.9360127 if dipstick protein is 0 or 1+, otherwise 0, + 0.770398. Probability = exp(logit) / (1 + exp(logit)). Urea in mmol/L is multiplied by 2.801 to reach BUN in mg/dL. Table 5 in the external biopsy cohort: at 5% sensitivity 0.94 and specificity 0.32; at 10% sensitivity 0.71 and specificity 0.63; at 25% sensitivity 0.27 and specificity 0.94. This is the development intercept, not the later prevalence shift of ln(local prevalence / 0.23). (2022)

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Clinical inputs

Serum creatinine before biopsy (mg/dL)Accepted range: 0.2 to 20
Blood urea nitrogen (mg/dL)Accepted range: 1 to 200
Urine dipstick specific gravityAccepted range: 1.001 to 1.04
Urine dipstick protein

Primary source

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