*! version 1.1.0 15July2011
help bronch

Title

bronch -- Calculates severity of illness in bronchiolitis using the National Children's Hospital
severity of bronchiolitis model, (NCH-SOB).

Syntax

bronch
[ work_of_breathing tachycardia age dehydration]
[, options]

bronchi
[ work_of_breathing tachycardia age dehydration]
[, options]

Main
nch uses coefficients based on an inpatient derivation dataset, the default

olhsc uses coefficients based on an emergency department validation dataset

printscreen sends the output to a printer

admit calculates the probability of admission

discharge calculates the probability of discharge

probabilities calculates the probability of a patient falling into another severity category

Description

bronch calculates the severity of illness for infants presenting with bronchiolitis. It relies on four variables
age(in months), dehydration classified as none(0) mild(1) moderate(2) or severe(3), tachycardia (heart
rate at or above the 98th centile for age), Increased work of breathing defined as (1)for moderate or severe increase in
work of breathing and (0) otherwise.

This command categorizes bronchiolitis severity as mild, moderate or severe using an ordinal logistic regression
model. bronch expects data in the wide format i.e. one observation per row and all the required
variables in that row. When issuing bronch the order in which the variables are specified matters. After executing bronch
stata issues a warning to the user reminding them which variable has been used
to specify each component in the model. It is the user's to ensure that
they have correctly specified the variables used to calculate the score.

Options

Main

nch uses coefficients based on an inpatient derivation dataset. This is the default.
The coefficients (odds ratio)for this option are as follows. Age *** ()per month, Dehydration ***()
per step increase from none,mild, moderate, severe, Tachycardia ** (), Increased work of breathing** ()

olhsc uses coefficients based on an emergency department validation dataset. The coefficients
(odds ratio)for this option are as follows. Age *** ()per month, Dehydration ***()
per step increase from none,mild, moderate, severe, Tachycardia ** (), Increased work of breathing** ()

probabilities calculates the proabability for each observation falling within each bronchiolitis
severity classification (mild, moderate, severe). This option creates three new variables for each observation
_pmild _pmoderate and _psevere containing the values for the mild moderate and severe categories respectively.

admit calculates the proabability for each observation of not having mild disease. This is the probability
of admission when using the ohlsc option and the probability of being discharged in less than one day with
the nch option. This option creates a new variable for each observation _padmit.

printscreen sends the output to the screen.

generate(newvar) creates newvar containing the value for bronchiolitis severity.If not specified the
default is bronch.

Saved Results

Support

_bronch contains the severity of bronchiolitis (i.e. mild, moderate, or severe)

_pmild contains the probability of mild disease

_pmoderate contains the probability of moderate disease

_psevere contains the probability of severe disease

_tachycardia_product contains the product of the coeficient (odds ratio) of tachycardia and the record value for each observation

_age_product contains the product of the coeficient (odds ratio) of age and the record value for each observation

_dehydration_product contains the product of the coeficient (odds ratio) of dehydration and the record value for each observation

_work_of_breathing_product contains the product of the coeficient (odds ratio) of work of breathing and the record value for each observation

_Z contains the summation of the products of the four parameters for each observation

_Z_difference_Zi_k1 contains the data that corresponds to mild disease for each observation

_difference_Zi_k2 contains the data that corresponds to both mild and moderate disease for each observation

_probability_Zi_k2 contains the combined probability of mild and moderate disease for each observation

_logit1_1 contains the probability of mild disease

_logit2_1 contains the probability of moderate disease

_logit3_1 contains the probability of severe disease

_padmit contains the probability of admission using anything greater than mild disease as a surrogate marker for a patient that should be admitted

_discharge contains the probability of discharge using mild disease as a surrogote marker for a dischargable patient

_wob_processed contains a simplified version of the mapped work of breathing data

_wob_processed_mod contains the mapped work of breathing data as described in the algorithm in reference 1

_age_processed contains the mapped age data as described in the algorithm in reference 1

_dehyd_processed contains the mapped dehydration data as described in the algorithm in reference 1

_tachy_processed contains the mapped tachycardia data as described in the algorithm in reference 1

_missing_wob contains the number of observation with missing data for work of breathing

_missing_age contains the number of observation with missing data for age

_missing_tachy contains the number of observation with missing data for tachycardia

_missing_dehydration contains the number of observation with missing data for dehydration

_valid_calculation contains the number of observation with valid data

Remarks

The NCH-SOB was derived in one childrens hospital where mild was defined as immediate
discharge on review of the resident admission by an attending pediatrician, moderate as
hospital admission less than and including median length of stay, and severe disease as
admission greater than the median length of stay. The model was validated in another
childrens hospital Emergency Department. In the validation 'mild' severity was based on
actual discharge from the pediatric emergency room by a resident with at least five years
post graduate training. 'Moderate' disease was defined as hospital admission less than and
including median length of stay, and 'severe' disease as admission for greater than the
median length of stay. The median length of stay was the same in both derivation and
validation phases.

Both models satisfied the proportional odds assumption. Users may select which coefficents
to use based on whether they are dealing primarily with inpatient or outpatient data. Full
details of the model used in this severity of illness classification tool can be found in
reference 1.

Examples

. bronchi mild 150 2 mild

. bronch work_of_breathing tachycardia age dehydration

. bronch work_of_breathing tachycardia age dehydration , olhsc prob admit

. bronch work_of_breathing tachycardia age dehydration, by(gender)

Authors

Carl E. Mitchell
Department of Emergency Medicine
Kern Medical Center
Bakersfield, CA 93306

Paul Walsh
Department of Emergency Medicine
Kern Medical Center
Bakersfield, CA 93306

References

Walsh, P. Rothenberg, S.J., O'Doherty, S., Hoey, H. and Healy, R. 2004 A validated clinical
model to predict the need for admission and length of stay in children with acute
bronchiolitis. European Journal of Emergency Medicine 11:5 265-72