calculating-weights-and-heights.md

Weight-related items

Using the following SQL snippet, the item identifiers containing 'weight' in their label were queried.

SELECT itemid, label
FROM mimiciii.d_items
WHERE LOWER(label) LIKE '%%weight%%'
-- Query complete in 00:00:00.102

The query results were as follows:

itemid	label
580	Previous Weight
581	Previous WeightF
4183	Birthweight (kg)
733	Weight Change
763	Daily Weight
3580	Present Weight (kg)
3581	Present Weight (lb)
3582	Present Weight (oz)
3583	Previous Weight (kg)
3692	Weight Change (gms)
3693	Weight Kg
3723	Birth Weight (kg)
7000	ideal body weight
45271	Chucks Pad Weight
226846	Feeding Weight
224639	Daily Weight
227854	Weight Bearing Status
226512	Admission Weight (Kg)
226531	Admission Weight (lbs.)
225124	Unintentional weight loss >10 lbs.
226740	APACHE II Diagnosistic weight factors - Medical
226741	APACHE II Diagnosistic weight factors - Surgical emergency
226742	APACHE II Diagnosistic weight factors - Surgical

Item selection

From this query, the following items were selected for relevance to patient weight:

itemid	label
580	Previous Weight
581	Previous WeightF
763	Daily Weight
224639	Daily Weight
226512	Admission Weight (Kg)
226531	Admission Weight (lbs.)
226846	Feeding Weight

The item identifiers were hard coded into the weights querying logic.

WEIGHT_ITEM_IDS = (580, 581, 763, 226846, 224639, 226512, 226531)

Units of measure

The units of measure for all selected item identifers are kilograms, with the exception of 226531 which is in pounds. To enable conversion, the conversion factor to the kilogram was declared for each item identifier:

WEIGHT_CONVERSION_FACTORS = {
    580: 1,
    581: 1,
    763: 1,
    224639: 1,
    226512: 1,
    226531: 0.45359237,
    226846: 1
}

Height-related items

Carrying out the same process for height-related items involved the following SQL snippet:

SELECT itemid, label
FROM mimiciii.d_items
WHERE LOWER(label) LIKE '%%height%%'
-- Query complete in 00:00:00.048

Item selection

The query results were as follows:

itemid	label
216	Height of Bed
1394	Height Inches
226707	Height
226730	Height (cm)

Units of measure

To investigate the units of measure for each of these items, the following query was used, where ITEM_ID is the item identifier.

SELECT DISTINCT valueuom
FROM mimiciii.chartevents
WHERE itemid IN (ITEM_ID)
-- Query complete in 00:00:00.042

Final selection

From these items, the following were selected as relevant to patient height, along with the conversion factor to metres:

itemid	label	Conversion factor to metres
1394	Height Inches	0.0254
226707	Height	0.0254
226730	Height (cm)	0.01

The item identifiers were hard coded into the heights querying logic.

HEIGHT_ITEM_IDS = (1394, 226707, 226730)
HEIGHT_CONVERSION_FACTORS = {
    1394: 0.0254,
    226707: 0.0254,
    226730: 0.01
}