# Reference SQL (matched-content control)

The following block is the public reference SQL used to construct the
ground truth for this task. It is provided verbatim, without procedural
prose, to test whether matched task-relevant content alone explains the
WITH-SKILL gain.

```sql
-- ------------------------------------------------------------------
-- Title: KDIGO Acute Kidney Injury (AKI) staging
-- This query extracts the maximum KDIGO AKI stage for each ICU stay
-- within the first 48 hours of admission. KDIGO stages range 0-3
-- based on creatinine changes, urine output rates, and CRRT.
-- ------------------------------------------------------------------

-- Reference for KDIGO:
--    Kidney Disease: Improving Global Outcomes (KDIGO) Acute Kidney
--    Injury Work Group. "KDIGO Clinical Practice Guideline for Acute
--    Kidney Injury." Kidney Int Suppl. 2012;2:1-138.

-- Aggregates the time-series kdigo_stages table to one row per ICU stay.
-- Takes the maximum stage across all measurement times within 48h.

SELECT
    ie.subject_id, ie.hadm_id, ie.stay_id
    , COALESCE(MAX(k.aki_stage), 0) AS aki_stage
    , COALESCE(MAX(k.aki_stage_creat), 0) AS aki_stage_creat
    , COALESCE(MAX(k.aki_stage_uo), 0) AS aki_stage_uo
    , COALESCE(MAX(CASE WHEN k.aki_stage_crrt > 0 THEN 3 ELSE 0 END), 0) AS aki_stage_crrt
FROM mimiciv_icu.icustays ie
LEFT JOIN mimiciv_derived.kdigo_stages k
    ON ie.stay_id = k.stay_id
    AND k.charttime >= ie.intime
    AND k.charttime <= ie.intime + INTERVAL '48' HOUR
GROUP BY ie.subject_id, ie.hadm_id, ie.stay_id
;
```
