Table 1.

Inclusion and exclusion criteria for reviewed studies

Inclusion	Exclusion
Study design
We included articles from the year 2000 to 31 Dec 2016, without any restriction on study design. We only included original primary studies published in peer-reviewed journals. Only studies in English were included.	We excluded reviews, commentaries, letters, issue briefs, editorials, poster presentations, or conference papers.
Populations and settings
We included articles without any restriction on populations and settings (ie, included low-middle income countries, developed countries, any age groups, etc).	NA
Intervention
Subjects with non-communicable disease (NCD) multimorbidity.	Subjects with single chronic diseases and/or infectious diseases.
Comparator
Not applicable in this review.
Outcome: OOPE on medicines for multimorbidity
1. First, we ensured the type of expenditure studied in the article was OOPE borne by patients. We defined OOPE as spending that was not reimbursed, but directly incurred by the patient from their income, as a proportion of household expenditures, or from cost sharing from insurance. OOPE did not include expenditure on insurance premiums.	1. Articles not on OOPE were excluded: for example, articles on national healthcare spending, or expenditure by insurance companies, instead of OOPE by individuals.
2. Second, we ensured OOPE was for medicines. Medicines could be for treatment of chronic conditions, including prescription drugs, non-prescription drugs, medications, pharmaceuticals, alternative medicines, and complementary medicines.	2. Articles that only studied total inpatient costs, or total outpatient costs, even though it incorporated costs of medicines, were excluded.
3. Thirdly, we ensured OOPE on medicines was compared for different numbers of multimorbidities. Articles must specify OOPE on medicines for different numbers of NCDs, or different combinations of NCDs that consisted of different numbers of NCDs. For example, article compares OOPE on medicines for 0, 1, 2–3, 4–6 NCDs, or article compares OOPE on medicines for diabetes (ie, 1 NCD) and diabetes with arthritis and depression (ie, 3 NCDs).	3. OOPE on medicines not studied in association with specific numbers of NCDs. For example, OOPE was studied in associated with Charlson-comorbidity Index instead of number of NCDs.

OOPE, out-of-pocket expenditure.