{"uid":"cap_gfrb0_154rn6UivrJCAv1","slug":"ckid-u25-egfr-calculator-pierce-2021-2d9c9c2a","name":"CKiD U25 eGFR Calculator (Pierce 2021)","description":"CKiD U25 eGFR (Pierce 2021) for ages 1-25: age- and sex-dependent K times height in meters over creatinine (mg/dL), or K over cystatin C (mg/L), or the average of both when both markers are given. Height may be cm or inches; creatinine may be mg/dL or µmol/L. Not the Schwartz 2009 bedside 0.413 formula, not a drug dose, and not a CKD stage. Not a medical device.","url":"https://api.magentlab.com/api/calc/ckid_u25","method":"GET","headers":{},"bodySchema":{"type":"object","$schema":"https://json-schema.org/draft/2020-12/schema","required":["input"],"properties":{"input":{"type":"object","required":["type","method"],"properties":{"type":{"type":"string","const":"http"},"method":{"enum":["GET","HEAD","DELETE"],"type":"string"},"headers":{"type":"object","additionalProperties":{"type":"string"}},"queryParams":{"type":"object","required":["age_years","sex"],"properties":{"sex":{"enum":["female","male"],"type":"string","description":"Sex used by Pierce 2021 Table 2 K. female or male."},"age_years":{"type":"number","description":"Age in years (1-25, fractional ages allowed). Pierce 2021 CKiD U25 age-dependent K is evaluated at that age. Not the adult 18-120 clamp."},"height_cm":{"type":"number","description":"Height in centimeters (50-250). Required with creatinine for the creatinine or combined path. Converted to meters in the equation. Provide height_cm or height_in. Not required for cystatin-only."},"height_in":{"type":"number","description":"Height in inches (20-98). Converted as cm = in * 2.54."},"cystatin_c_mg_l":{"type":"number","description":"Serum cystatin C in mg/L (0.2-10). Required for the cystatin-only or combined path. Height is not required when this is the only marker."},"creatinine_mg_dl":{"type":"number","description":"Serum creatinine in mg/dL (0.1-20). Required with height for the creatinine or combined path. Provide this or creatinine_umol_l."},"creatinine_umol_l":{"type":"number","description":"Serum creatinine in µmol/L (9-1768). Converted as mg/dL = µmol/L / 88.42."}}}},"additionalProperties":false},"output":{"type":"object","required":["type"],"properties":{"type":{"type":"string"},"example":{"type":"object"}}}}},"responseSchema":null,"example":null,"exampleRequest":null,"tags":["x402"],"displayCostAmount":"0.005","displayCostAsset":"USDC","priceDynamic":false,"priceHint":null,"priceStatus":"priced","priceSource":"probe","requiresHandshake":false,"reviewCount":0,"rating":{"score":"0.00","successRate":"0.00","reviews":0,"stars":null,"state":"unrated"},"availabilityStatus":"unknown","priceObserved":null,"sessionDeposit":null,"pricing":{"kind":"static","summary":"$0.005/call","primary":{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"},"accepted":[{"kind":"static","protocol":"x402","network":"base","amountUsd":"0.005","per":"call","confidence":"exact"}]},"paymentMethods":[{"uid":"pm_15BcXJ3z9N47tGJeYA71Z","protocol":"x402","methodType":"crypto","chain":"base","mode":"charge","costAmount":"0.005","costPer":"request","priority":0,"asset":"0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913","unit":"request","depositMicros":null,"planRef":null}],"brandName":null,"brandSlug":null,"brandBaseUrl":null,"brandDocsUrl":null,"whatItDoes":"Calculates estimated GFR for patients aged 1–25 using the Pierce 2021 CKiD U25 formula with creatinine, cystatin C, or both markers","exampleAgentPrompt":"Calculate the CKiD U25 eGFR for a 12-year-old male who is 145 cm tall with a serum creatinine of 0.7 mg/dL and a cystatin C of 0.9 mg/L using the Pierce 2021 formula.","exampleUseCases":[{"title":"Pediatric CKD workup with dual markers","prompt":"My patient is a 9-year-old female, 130 cm tall, with a creatinine of 0.6 mg/dL and cystatin C of 1.1 mg/L — can you run the Pierce 2021 CKiD U25 eGFR using both markers?"},{"title":"Adolescent cystatin-C-only eGFR","prompt":"Calculate the CKiD U25 eGFR for a 17-year-old male using only his cystatin C result of 1.4 mg/L — we don't have a reliable creatinine for him."},{"title":"Young adult creatinine-based renal estimate","prompt":"What is the Pierce 2021 CKiD U25 eGFR for a 22-year-old female who is 63 inches tall and has a serum creatinine of 1.2 mg/dL?"}],"resultDescription":"Returns a numeric eGFR estimate (mL/min/1.73m²) computed via the Pierce 2021 CKiD U25 age- and sex-dependent K formula. When both creatinine and cystatin C are provided, returns the average of both eGFR paths. Indicates which calculation path was used (creatinine-based, cystatin C-based, or combined).","failureModes":["Age outside the 1–25 year range returns a validation error","Missing required paired inputs (e.g., creatinine without height) returns an error","Creatinine or cystatin C values outside plausible ranges (e.g., creatinine > 20 mg/dL) may be rejected","Invalid sex enum value returns a schema error","Providing neither creatinine nor cystatin C returns an error — at least one marker is required"],"whenToPreferThis":"Use this endpoint when you need the Pierce 2021 CKiD U25 eGFR specifically for patients aged 1–25, as opposed to the adult Schwartz bedside 0.413 formula or adult CKD-EPI equations. It is particularly appropriate when the patient age falls outside the adult range or when you have cystatin C available for a more accurate combined estimate. Do not use for CKD staging, drug dosing decisions, or patients over 25.","instructions":null,"reviewSummary":null,"reviewSummaryHighlights":null,"reviewSummaryConcerns":null,"reviewSummaryGeneratedAt":null,"activationCount":0,"lastUsedAt":null,"lastSuccessfullyRanAt":null,"lastHealthCheckAt":"2026-09-14T07:12:38.605Z","isFirstParty":false}