Appendix Table 4. Relevant candidate patient subgroups, effect modifiers, for targeting the initiative and their data elements.

Relevant subgroup	Data Elements
(1) Primary language*	Primary language is English, Spanish
(2) Primary care vs specialty practices	Internal medicine or family medicine versus allergy-immunology or pulmonary
(3) Age	18-39 years, 40-49 years, ≥ 50 years
(4) Skills that would support use of portal and asthma self-management	Numeracy† Literacy-reading comprehension† Education Computer literacy (Electronic Health Literacy Scale† Inhaler technique‡
(5) Social Community barriers	Food or clothing inadequacy MOS Social Support§ Exposure to Violence∥
(6) Trust of patient portal	Patient portal preserves privacy¶
(7) Depression and chronic disease load	Depression** Diabetes Hypertension High cholesterol Obesity Cancer Current Smoker
(8) Asthma severity	Hospitalizations ED visits Intubation Years taking ICS Prednisone (Days/week)
(9) Home environment	Crowding at home (number of rooms, number of people at home) Been without housing in last 6 months Utilities shut off in the last 6 months Times moved in last 12 months Exposure to second hand smoke

^*Primary language was self-reported: English, Spanish.

^†Three literacy measures were used: Asthma Numeracy Questionnaire for numeracy,¹³ the Short Test of Functional Health Literacy in Adults¹² for reading comprehension, and an item from the Electronic Health Literacy Scale: “I feel confident in using information from the internet to make health decisions.”¹⁴

^‡Inhaler technique consisted of items from the Expert Panel Report²⁴ and manufacturers’ instructions that were common to the type of inhaler, metered dose or dry powder inhaler. Inhaler technique was measured using a 7-point scale for a metered dose inhaler and a 6-point scale for a dry powder inhaler, testing the patient using the inhaler used for the patient’s inhaled steroid.

^§Social Support was measured with MOS Social Support Study.²⁵

^∥Exposure to violence was measured with a question adapted from Wright et al.^8,26

^¶Privacy concerns with the patient portal assessed using the Portal Use Baseline Survey (“I am concerned about looking up my personal health information on the internet” with a Likert 5-point response.)

^**Depression as measured by the Center for Epidemiologic Studies Depression Scale, a validated 20-item scale.¹⁵