Fix KDIGO AKI Stage 3 SCr criterion to use a +0.3 increase instead of hardcoded 3.7

[Chessing234]

Bug

In kdigo_stages.sql, the creatinine-based AKI Stage 3 branch for patients reaching SCr >= 4.0 mg/dL is meant to require an acute increase of >= 0.3 within 48 hours (or >= 1.5x baseline), per the KDIGO 2012 AKI guideline (p.21). It is implemented as:

when cr.creat >= 4
  and (cr.creat_low_past_48hr <= 3.7 OR cr.creat >= (1.5*cr.creat_low_past_7day))
  then 3

Root cause

The hardcoded creat_low_past_48hr <= 3.7 only encodes a 0.3 increase when creat is exactly 4.0 (4.0 − 3.7 = 0.3). For any creatinine above 4.0 the test no longer matches the intended threshold. For example, creat = 5.0 with a 48h low of 3.8 is a real increase of 1.2 mg/dL — clearly Stage 3 — yet 3.8 <= 3.7 is false and the 1.5x-baseline arm may also fail, so the patient is not flagged.

Fix

Replace the hardcoded 3.7 with the actual >= 0.3 increase condition, matching the comment directly above it:

and (cr.creat >= (cr.creat_low_past_48hr + 0.3) OR cr.creat >= (1.5*cr.creat_low_past_7day))

This is the change confirmed by the maintainer in #1357. Applied to both the MIMIC-IV and MIMIC-III BigQuery source files (the reporter noted both are affected). The concepts_postgres/concepts_duckdb copies are auto-generated from these sources and should be regenerated via the conversion scripts.

Fixes #1357