baseline-creatinine

Baseline Creatinine Estimation

Estimates the patient's baseline (pre-illness) serum creatinine, which is critical for accurate AKI staging. The true baseline is often unknown; this query uses a hierarchical approach.

M4Bench Use

In M4Bench, target concept tables listed in the task configuration are removed or unavailable in the agent database. Use this skill as procedural guidance and derive the requested output from available source or intermediate tables; do not rely on a precomputed target table or bundled SQL script.

When to Use This Skill

• KDIGO AKI staging (requires baseline comparison)
• AKI research cohorts
• Chronic kidney disease identification
• Renal function trajectory analysis

Baseline Determination Rules

The baseline creatinine is determined hierarchically:

1. If lowest admission creatinine <= 1.1 mg/dL: Use the lowest value (assumed normal)
2. If patient has CKD diagnosis: Use the lowest admission value (even if elevated)
3. Otherwise: Estimate baseline using MDRD equation assuming GFR = 75 mL/min/1.73m^2

MDRD Estimation Formula

For patients without normal creatinine and without CKD, baseline is estimated:

Male patients:

scr_baseline = (75 / 186 / age^(-0.203))^(-1/1.154)

Female patients:

scr_baseline = (75 / 186 / age^(-0.203) / 0.742)^(-1/1.154)

This back-calculates creatinine assuming eGFR = 75 mL/min/1.73m^2 (lower limit of normal).

CKD Identification

CKD is identified from ICD codes:

• ICD-9: 585 (Chronic kidney disease)
• ICD-10: N18 (Chronic kidney disease)

Critical Implementation Notes

1. Adults Only: Query filters to age >= 18 (pediatric creatinine norms differ).

2. MDRD Limitations:

   • Less accurate in elderly, extremes of body size, or certain ethnicities
   • Assumes GFR = 75, which may underestimate for young healthy patients

3. Admission Bias: Using admission creatinine as baseline may underestimate for patients admitted already in AKI (AKI-on-admission).