Table 2 Health system functions of CHWs

1. Deliver diagnostic, treatment, and other clinical services

• Identify and assess sick community members: Use rapid tests for malaria [21, 61, 76] and HIV [32, 77]; determine if a child’s breathing is dangerously rapid [78], identify high-risk pregnancies [42]; monitor clinical symptoms and signs of drug toxicity in people living with HIV and refer when appropriate [52], monitor the effects of mental-health-related medications [54]; conduct breast-cancer screening exams [79], measure and monitor blood pressure [43]

• Provide medicines and other pharmaceuticals: Dispense contraceptives [80]: administer injectable contraceptives [81]; distribute antiretroviral drugs [52], iron folic acid tablets [82], vitamin A [82] or antimalarials [33, 82]

• Directly provide care and treatment: Perform home deliveries [15, 22, 83]; vaccinate children [16]; provide community-level diagnosis and treatment for pneumonia, malaria, and other infectious diseases [84]

2. Assist with appropriate utilization of health services, make referrals

Help ethnic minorities in the USA make and keep medical appointments for cancer screening [87] or for diabetes management [88], help people with hypertension in the USA access health insurance [43], help pregnant women with birth planning and preparedness to facilitate institutional delivery [91, 92], mobilize communities around maternal and neonatal health practices [93], refer women to health facilities for delivery [82, 94], encourage access and adherence to HIV care [32, 39, 95, 96], or find underserved groups and encourage them to have their children immunized [20]

3. Provide health education and behavior change motivation to community members

Provide education to reduce HIV stigma [50] or promote behaviors that reduce risk of acquiring HIV [74]; assist with family planning [80], depression, or assessment of child mental development [97]; encourage physical activity among those with non-communicable disease [98]; promote exclusive breastfeeding [82], antenatal and postnatal care and family planning [82]; advise on tetanus vaccination [82] or family planning [82]; provide education on cancer [87, 99], hypertension [43] and diabetes [89, 100]; reduce childhood asthma-triggering behaviors and environmental pathogens that provoke asthma [56, 57]

4. Collect and record data

Perform general clerical duties [70] and data collection (including using mHealth tools [101, 102]), identify and report on malaria outbreaks [44], monitor medicine stocks and notify government agencies when stocks are low [44, 76]

5. Improve relationships between health services and communities

Act as mediators between individuals and health services (e.g., to improve provider responsiveness to patient needs) [43], act as cultural mediators [51] (e.g., between Aboriginals and non-Aboriginals in Australia [45]), serve as patient advocates (e.g., for those with diabetes [89, 90] or cancer [87] in the USA, or for mental healthcare in LMICs [51, 103]); serve as community advocates (e.g. for Latino communities in the USA [104])

6. Provide psychosocial support

Form support groups for people with HIV [14, 50] or women [93, 105]; provide anti-retroviral treatment adherence reminders [50]; provide one-to-one psychosocial support to reduce maternal depression [73, 106], for people with hypertension [43], or for USA Latino parents of youth with mental health issues [106]; support adherence to drug regimens by sending short messages to cell phones to remind people living with HIV to take their medication [107]