This systematic review was conducted based on the preferred reporting items for systematic reviews and meta-analyses (PRISMA) guidelines. A systematic review method was selected to allow a robust and reproducible approach to structure a critical synthesis of the existing and current evidence. Considering the urgency of the matter and limited available evidence on the topic, we did not register the systematic review protocol.
Search strategy and data sources
Five online databases, included PubMed, Scopus, Embase, Web of Science and Science Direct, were searched to identify relevant and published studies. The search was conducted on Titles and Abstracts. A preliminary search in March 26, 2020 identiﬁed a range of available evidence on the role of telehealth services during 2019 novel coronavirus (COVID-19) outbreak. A subsequent search was conducted on April 3, 2020 to update the results. The combination of keywords and Medical Subject Headings (MeSH) were used: COVID19, COVID-19, Coronavirus, Novel coronavirus, 2019-nCoV, Wuhan coronavirus, SARS-CoV-2, SARS2, Tele*, Telemedicine, Tele-medicine, Telehealth, Tele-health, Telecare, Mobile Health, mHealth, Electronic health, and ehealth. The Boolean operators (AND, OR and NOT) were used to combine terms. A librarian was consulted during this phase to ensure that the search strategy was satisfactory. The search in each database was adapted accordingly. For example, the search strategy in the PubMed database was executed as follows:
(COVID-19[title/abstract] OR COVID19[title/abstract] OR Coronavirus[title/abstract] OR Novel coronavirus[title/abstract] OR 2019-nCoV[title/abstract] OR Wuhan coronavirus[title/abstract] OR SARS-CoV-2[title/abstract] OR SARS2[title/abstract]) AND (Telemedicine[title/abstract] OR Tele-medicine[title/abstract] OR Telehealth[title/abstract] OR Tele-health[title/abstract] OR Telecare[title/abstract] OR Mobile health[title/abstract] OR mHealth[title/abstract] OR Electronic health[title/abstract] OR eHealth[title/abstract]).
Manual search in web-based resources was performed on Google, Google Scholar, journals which published key articles and through searching specific website (WHO, https://www.who.int, Centers for Disease Control and Prevention, https://www.cdc.gov, National Institute for Health and Clinical Excellence, https://www.nice.org.uk, National Health Commission of the People’s Republic of China http://www.nhc.gov and National Administration of Traditional Chinese Medicine http://www.satcm.gov.cn). In addition, we reviewed the references of the selected articles in order to identify additional studies or reports not retrieved by the preliminary searches (reference by reference).
All studies with primary sources of evidence reporting the role of telehealth services in COVID-19 were included in our analyses. In fact, studies were included if they clearly defined function type of telehealth in diagnosis, management, prevention and treatment of COVID-19, published from December 31, 2019 to April 3, 2020 , were written in English language and published in peer reviewed journals. The reason for choosing December 31 was due to the fact that this date coincides with the emergence of COVID-19 in Wuhan, Hubei Province, China. Actually, all studies illustrating any sorts of using telehealth tools in all aspects of health care (primary, secondary or tertiary level health care) to provide clinical services, diagnosis of clinical education, assessment of symptoms, triage of patients, consultation services, and training or supervision of clinicians were included. Studies about other technologies (e.g. Internet of Medical Things or IoMT), duplicate publications, review articles, opinion articles, and letters not presenting original data were excluded, as well as studies reporting incomplete information.
Study selection and data extraction
Two authors (A.H. and E.M.) who performed the literature search also independently followed the application of the inclusion and exclusion criteria and screened the studies based on the titles and abstracts. After initial screening, full-text of studies were obtained and examined to ensure eligibility for the development of the data extraction form.
Data were extracted for all papers which met the eligibility and inclusion criteria for the review. The following data were extracted and analyzed: first author, date of publication, country, design of study, type of used telehealth, key outputs of studies and effects of telehealth.
To assess the quality of the included studies, the Critical Appraisal Skills Program (CASP) checklists were adopted. The CASP tools were developed to teach people how to critically appraise different types of evidence (31). For scoring the quality of the included studies, they were divided into three categories of poor, medium, and good quality.
For expressing and synthesizing the results of the included studies, narrative synthesis of overall evidence was undertaken by comparing and contrasting the data. Three stages of the narrative synthesis included the development of a preliminary synthesis, exploration of the relationships within and between studies and the determination of the robustness of the synthesis (32). Data of the included studies was qualitatively described and presented. The authors met frequently to discuss and reach consensus on the findings.