Fix KDIGO Stage 3 using hardcoded 3.7 instead of dynamic creatinine check

The 48-hour acute rise criterion compared creat_low_past_48hr against
the hardcoded value 3.7 (i.e. 4.0 - 0.3), which is only correct when
creatinine equals exactly 4.0. Replace with the dynamic expression
cr.creat >= (cr.creat_low_past_48hr + 0.3) to correctly evaluate the
>=0.3 acute increase for any creatinine value >=4.0.

Fixes #1357

Author: Chessing234

mimic-iii/concepts/organfailure/kdigo_stages.sql

@@ -17,7 +17,7 @@ with cr_stg AS
         -- For patients reaching Stage 3 by SCr >4.0 mg/dl
         -- require that the patient first achieve ... acute increase >= 0.3 within 48 hr
         -- *or* an increase of >= 1.5 times baseline
-        and (cr.creat_low_past_48hr <= 3.7 OR cr.creat >= (1.5*cr.creat_low_past_7day))
+        and (cr.creat >= (cr.creat_low_past_48hr+0.3) OR cr.creat >= (1.5*cr.creat_low_past_7day))
             then 3 
         -- TODO: initiation of RRT
         when cr.creat >= (cr.creat_low_past_7day*2.0) then 2

mimic-iv/concepts/organfailure/kdigo_stages.sql

@@ -20,7 +20,7 @@ WITH cr_stg AS (
                 --      an acute increase >= 0.3 within 48 hr
                 --      *or* an increase of >= 1.5 times baseline
                 AND (
-                    cr.creat_low_past_48hr <= 3.7 OR cr.creat >= (
+                    cr.creat >= (cr.creat_low_past_48hr + 0.3) OR cr.creat >= (
                         1.5 * cr.creat_low_past_7day
                     )
                 )