Forecasting Future Asthma Hospital Encounters of Patients With Asthma in an Academic Health Care System: Predictive Model Development and Secondary Analysis Study

Background Asthma affects a large proportion of the population and leads to many hospital encounters involving both hospitalizations and emergency department visits every year. To lower the number of such encounters, many health care systems and health plans deploy predictive models to prospectively identify patients at high risk and offer them care management services for preventive care. However, the previous models do not have sufficient accuracy for serving this purpose well. Embracing the modeling strategy of examining many candidate features, we built a new machine learning model to forecast future asthma hospital encounters of patients with asthma at Intermountain Healthcare, a nonacademic health care system. This model is more accurate than the previously published models. However, it is unclear how well our modeling strategy generalizes to academic health care systems, whose patient composition differs from that of Intermountain Healthcare. Objective This study aims to evaluate the generalizability of our modeling strategy to the University of Washington Medicine (UWM), an academic health care system. Methods All adult patients with asthma who visited UWM facilities between 2011 and 2018 served as the patient cohort. We considered 234 candidate features. Through a secondary analysis of 82,888 UWM data instances from 2011 to 2018, we built a machine learning model to forecast asthma hospital encounters of patients with asthma in the subsequent 12 months. Results Our UWM model yielded an area under the receiver operating characteristic curve (AUC) of 0.902. When placing the cutoff point for making binary classification at the top 10% (1464/14,644) of patients with asthma with the largest forecasted risk, our UWM model yielded an accuracy of 90.6% (13,268/14,644), a sensitivity of 70.2% (153/218), and a specificity of 90.91% (13,115/14,426). Conclusions Our modeling strategy showed excellent generalizability to the UWM, leading to a model with an AUC that is higher than all of the AUCs previously reported in the literature for forecasting asthma hospital encounters. After further optimization, our model could be used to facilitate the efficient and effective allocation of asthma care management resources to improve outcomes. International Registered Report Identifier (IRRID) RR2-10.2196/resprot.5039

Ethnicity (Hispanic or non-Hispanic); gender; age; marital status (married, single, partnered, divorced, widowed, or separated); race; and language. Features related to laboratory tests No. of laboratory tests; no. of laboratory tests having abnormal results; no. of days from the most recent laboratory test; whether an immunoglobulin E (IgE) test was performed; whether the greatest total serum IgE level is abnormally high; the greatest total serum IgE level; the largest percentage of blood eosinophils; and the largest blood eosinophil count. Features related to vital signs The mean diastolic blood pressure; the mean heart rate; the mean systolic blood pressure; the highest diastolic blood pressure; the mean temperature; the highest systolic blood pressure; the greatest heart rate; the mean respiratory rate; the greatest respiratory rate; the highest temperature; the mean peripheral capillary oxygen saturation (SpO 2 ); the lowest SpO 2 ; the mean peak expiratory flow; the lowest peak expiratory flow; the relative change of weight = (the most recently documented weight / the first documented weight -1) × 100%; the largest body mass index (BMI); and the relative change of BMI = (the most recently documented BMI / the first documented BMI -1) × 100%. Features that are related to diagnoses and calculated solely on ICD-9 and ICD-10 diagnosis codes No. of ICD-9 and ICD-10 diagnosis codes; no. of years from the first encounter related to asthma in the data set; no. of primary or principal asthma diagnoses; no. of asthma diagnoses; whether the most recent asthma diagnosis is a primary or principal one; the severity of the most recent asthma diagnosis; the severity of the most severe asthma diagnosis; no. of diagnoses of asthma with status asthmaticus; no. of diagnoses of asthma with (acute) exacerbation; the exacerbation severity (uncomplicated, exacerbation, or asthmaticus) of the most recent asthma diagnosis; the greatest exacerbation severity of any asthma diagnosis; no. of days from the most recent asthma diagnosis; no. of days from the most recent diagnosis of asthma with (acute) exacerbation or status asthmaticus; no. of diagnoses of noncompliance with medication regimen; family history of asthma; chronic obstructive pulmonary disease; no. of years from the first encounter related to chronic obstructive pulmonary disease in the data set; esophagitis; allergic rhinitis; anxiety or depression; ischemic heart disease; eczema; gastroesophageal reflux; sleep apnea; gastrostomy tube; obesity; Alzheimer's or Parkinson's disease; upper respiratory tract infection; decreased tone; increased tone; cystic fibrosis; immunoglobulin A (IgA) deficiency; pneumonia; vocal cord dysfunction; psoriasis; anaphylaxis; vasculitis; cirrhosis; gastrointestinal bleeding; gastrointestinal obstruction; inflammatory bowel disease; mental disorder; breathing abnormality like dyspnea; pregnancy; vitamin D deficiency; myocardial infarction; folate deficiency; congestive heart failure; malignancy; peripheral vascular disease; dementia; peptic ulcer disease; cerebrovascular disease; substance use; rheumatic disease; diabetes with chronic complication; renal disease; diabetes without chronic complication; bronchopulmonary dysplasia; moderate or severe liver disease; mild liver disease; paraplegia or hemiplegia; acquired immunodeficiency syndrome; and metastatic solid tumor. Features that are related to diagnoses and calculated jointly on ICD-9 and ICD-10 procedure codes along with ICD-9 and ICD-10 diagnosis codes Tracheostomy.
Features that are related to diagnoses and calculated jointly on Current Procedural Terminology (CPT) and Healthcare Common Procedure Coding System (HCPCS) procedure codes along with ICD-9 and ICD-10 diagnosis codes Cataract; and sinusitis.

Features related to the problem list
No. of active problems; no. of active problems of wheezing; no. of active problems of asthma with (acute) exacerbations; no. of active problems of asthma; no. of active problems of obesity; no. of active problems of congestive heart failure; no. of active problems of sleep apnea; no. of active problems of hypertension; no. of active problems of chronic obstructive pulmonary disease; no. of active problems of rhinitis; no. of active problems of diabetes; no. of active problems of anxiety/depression; no.of active problems of gastroesophageal reflux disease; no. of active problems about smoking; and the priority of the last active problem of asthma. Features related to medications Total no. of medications ordered; no. of medication orders; total no. of differing medications ordered; total no. of medication refills permitted; total no. of units of medications ordered; total no. of asthma medications ordered; no. of asthma medication orders; total no. of differing asthma medications ordered; total no. of asthma medication refills permitted; total no. of units of asthma medications ordered; total no. of short-acting beta-2 agonists ordered; total no. of refills permitted for short-acting beta-2 agonists; total no. of units of short-acting beta-2 agonists ordered; total no. of systemic corticosteroids ordered; total no. of refills permitted for systemic corticosteroids; total no. of units of systemic corticosteroids ordered; no. of asthma reliever orders; total no. of asthma relievers ordered; total no. of refills permitted for asthma relievers; total no. of differing asthma relievers ordered; total no. of units of asthma relievers ordered; total no. of units of asthma relievers ordered that are neither short-acting beta-2 agonists nor systemic corticosteroids; total no. of asthma relievers ordered that are neither short-acting beta-2 agonists nor systemic corticosteroids; no. of asthma controller orders; total no. of asthma controllers ordered; total no. of units of asthma controllers ordered; total no. of differing asthma controllers ordered; total no. of refills permitted for asthma controllers; total no. of inhaled corticosteroids ordered; total no. of refills permitted for inhaled corticosteroids; total no. of units of inhaled corticosteroids ordered; total no. of mast cell stabilizers ordered; total no. of refills permitted for mast cell stabilizers; total no. of units of mast cell stabilizers ordered; whether nebulizer was used; total no. of nebulizer medications ordered; no. of nebulizer medication orders; total no. of units of nebulizer medications ordered; total no. of differing nebulizer medications ordered; total no. of refills permitted for nebulizer medications; and whether spacer was used. Features related to insurances Whether the patient had any public insurance on the last day; whether the patient had any private insurance on the last day; and whether the patient was paid by oneself or a charity on the last day. Features related to the patient's visit types No. of ED visits; no. of ED visits related to asthma; the most recent ED visit's length of stay; the mean length of stay of an ED visit; no. of visits; no. of outpatient visits to the patient's PCP; no. of outpatient visits; no. of outpatient visits whose primary diagnosis is asthma; no. of hospitalizations; the hospitalizations' total length; the mean length of a hospitalization; no. of hospitalizations, ED visits, and outpatient visits; no. of intensive care admissions; the most emergent admission type of all of the visits; the most recent visit's admission type (elective, urgent, emergency, or trauma); no. of major visits for asthma; and the most recent visit's type (ED visit, outpatient visit, or hospitalization). As in our prior paper [23], we defined a major visit for asthma as an ED visit having an asthma diagnosis code, a hospitalization having an asthma diagnosis code, or an outpatient visit having a primary diagnosis of asthma. An outpatient visit having only a secondary diagnosis of asthma was treated as a minor visit for asthma.

Features on visit status and appointment scheduling
The day of the week when the most recent ED visit began; no. of cancelled appointments; the most recent visit's discharge disposition location (home, left against medical advice, or other non-home location); no. of no shows; no. of times of leaving against medical advice; for the most recent visit, the time to the actual visit after making the request showing its urgency; across all of the visits, the shortest time to the actual visit after making the request; whether the most recent hospitalization came from the ED; no. of days from the most recent hospitalization; no. of visits having same day appointments; no. of days from the most recent ED visit; no. of days from the most recent outpatient visit; no. of days from the most recent ED visit on asthma; and no. of days from the most recent outpatient visit on asthma. Features describing the patient's care continuity degree No. of differing asthma medication prescribers; no. of differing EDs the patient went to; no. of differing medication prescribers; no. of differing providers the patient saw in outpatient visits; and no. of differing PCPs of the patient.
Features related to procedures Mechanical ventilation reflected by ICD-10 and ICD-9 procedure codes; no. of ICD-10 and ICD-9 procedure codes; no. of HCPCS procedure codes of home oxygen therapy; no. of CPT procedure codes of the fractional exhaled nitric oxide test; no. of CPT/HCPCS procedure codes; no. of CPT procedure codes of pulmonary function tests; and no. of CPT/HCPCS procedure codes of influenza vaccination.

Allergy features
Indicator of drug or material allergy; the greatest severity of the patient's drug or material allergies; indicator of environmental allergy; the greatest severity of the patient's environmental allergies; indicator of food allergy; the greatest severity of the patient's food allergies; and no. of the patient's allergies. Features related to pulmonary function tests The mean forced expiratory volume in 1 second (FEV1); and the lowest FEV1.

Features related to social behavior history
No. of fluid ounces of alcohol the patient consumed every week according to the most recent record; whether the patient was ever documented of consuming alcohol; whether the patient consumed alcohol according to the most recent record; the mean no. of fluid ounces of alcohol the patient consumed every week across all of the records; no. of alcohol drinks the patient consumed every week according to the most recent record; the mean no. of alcohol drinks the patient consumed every week across all of the records; no. of packs of cigarettes the patient consumed every day according to the most recent record; whether the patient was a smoker according to the most recent record; the mean no. of packs of cigarettes the patient consumed every day across all of the records; whether the patient was a former smoker according to the most recent record; no. of years the patient had smoked for according to the most recent record; no. of times the patient took illicit drugs every week according to the most recent record; whether the patient took any illicit drug according to the most recent record; the mean no. of times the patient took illicit drugs every week across all of the records; and whether the patient was ever documented of taking any illicit drug.

Provider features
We defined the patient's PCP known at the most recent clinic visit as the patient's current PCP. We considered the following PCP features: no. of years that the PCP had practiced at UWM for; the PCP's age; whether the patient is of the same gender as the PCP; the PCP's primary specialty; whether the PCP is a resident; the PCP's type (physician, nurse, physician assistant, or other); the PCP's clinician title (doctor of medicine, registered nurse, physician assistant, or other); the percentage of the PCP's asthmatic patients in the pre-index year incurring asthma hospital encounters in the index year; and no. of asthmatic patients of the PCP.