fix: refactor UO to better align with kdigo guidelines

Author: alistairewj

mimic-iv/concepts/organfailure/kdigo_stages.sql

@@ -43,12 +43,15 @@ WITH cr_stg AS
         WHEN uo.uo_rt_6hr IS NULL THEN NULL
         -- require patient to be in ICU for at least 6 hours to stage UO
         WHEN uo.charttime <= DATETIME_ADD(ie.intime, INTERVAL '6' HOUR) THEN 0
-        -- require the UO rate to be calculated over half the period
-        -- i.e. for uo rate over 24 hours, require documentation at least 12 hr apart
-        WHEN uo.uo_tm_24hr >= 11 AND uo.uo_rt_24hr < 0.3 THEN 3
-        WHEN uo.uo_tm_12hr >= 5 AND uo.uo_rt_12hr = 0 THEN 3
-        WHEN uo.uo_tm_12hr >= 5 AND uo.uo_rt_12hr < 0.5 THEN 2
-        WHEN uo.uo_tm_6hr >= 2 AND uo.uo_rt_6hr  < 0.5 THEN 1
+        -- require the UO rate to be calculated over duration specified in KDIGO
+        -- Stage 3: <0.3 ml/kg/h for >=24 hours
+        WHEN uo.uo_tm_24hr >= 24 AND uo.uo_rt_24hr < 0.3 THEN 3
+        -- *or* anuria for >= 12 hours
+        WHEN uo.uo_tm_12hr >= 12 AND uo.uo_rt_12hr = 0 THEN 3
+        -- Stage 2: <0.5 ml/kg/h for >= 12 hours
+        WHEN uo.uo_tm_12hr >= 12 AND uo.uo_rt_12hr < 0.5 THEN 2
+        -- Stage 1: <0.5 ml/kg/h for 6–12 hours
+        WHEN uo.uo_tm_6hr >= 6 AND uo.uo_rt_6hr  < 0.5 THEN 1
     ELSE 0 END AS aki_stage_uo
   FROM `physionet-data.mimiciv_derived.kdigo_uo` uo
   INNER JOIN `physionet-data.mimiciv_icu.icustays` ie

mimic-iv/concepts/organfailure/kdigo_uo.sql

@@ -73,24 +73,18 @@ select
 , ur.urineoutput_12hr
 , ur.urineoutput_24hr
 
--- calculate rates
--- we would like to improve the sensitivity of this calculation by:
--- (1) requiring UO documentation over at least N/2 hours
--- (2) excluding a rate if it was calculated over >>N hours
--- this is to remove cases where we have a very short measurement
---  (e.g. one UO measurement made for 1 hour determining the 6 hour rate)
--- and remove cases where we have very sparse measurements
---  (e.g. two UO measurements 12 hours apart used for the 6 hour rate calculation)
+-- calculate rates while requiring UO documentation over at least N hours
+-- as specified in KDIGO guidelines 2012 pg19
 , CASE
-  WHEN uo_tm_6hr > 3 AND uo_tm_6hr < 9
+  WHEN uo_tm_6hr >= 6 AND uo_tm_6hr < 12
   THEN ROUND(CAST((ur.urineoutput_6hr/wd.weight/uo_tm_6hr) AS NUMERIC), 4)
   ELSE NULL END AS uo_rt_6hr
 , CASE
-  WHEN uo_tm_12hr > 6 AND uo_tm_12hr < 18
+  WHEN uo_tm_12hr >= 12
   THEN ROUND(CAST((ur.urineoutput_12hr/wd.weight/uo_tm_12hr) AS NUMERIC), 4)
   ELSE NULL END AS uo_rt_12hr
 , CASE
-  WHEN uo_tm_24hr > 12 AND uo_tm_24hr < 36
+  WHEN uo_tm_24hr >= 24
   THEN ROUND(CAST((ur.urineoutput_24hr/wd.weight/uo_tm_24hr) AS NUMERIC), 4)
   ELSE NULL END AS uo_rt_24hr