title: Quasi-experiments to establish causal effects of HIV care and treatment and to improve the cascade of care.
abstract: OBJECTIVE
  Randomized, population-representative trials of clinical interventions are rare. Quasi-experiments have been used successfully to generate causal evidence on the cascade of HIV care in a broad range of real-world settings.
  
  
  RESULTS
  Quasi-experiments exploit exogenous, or quasi-random, variation occurring naturally in the world or because of an administrative rule or policy change to estimate causal effects. Well designed quasi-experiments have greater internal validity than typical observational research designs. At the same time, quasi-experiments may also have potential for greater external validity than experiments and can be implemented when randomized clinical trials are infeasible or unethical. Quasi-experimental studies have established the causal effects of HIV testing and initiation of antiretroviral therapy on health, economic outcomes and sexual behaviors, as well as indirect effects on other community members. Recent quasi-experiments have evaluated specific interventions to improve patient performance in the cascade of care, providing causal evidence to optimize clinical management of HIV.
  
  
  CONCLUSIONS
  Quasi-experiments have generated important data on the real-world impacts of HIV testing and treatment and on interventions to improve the cascade of care. With the growth in large-scale clinical and administrative data, quasi-experiments enable rigorous evaluation of policies implemented in real-world settings.
authors.affiliation: aDepartment of Global Health, Boston University School of Public Health, Boston, Massachusetts, USA bHealth Economics and Epidemiology Research Office, University of Witwatersrand, Johannesburg, South Africa cDepartment of Global Health and Population, Harvard T.H. Chan School of Public Health dDepartment of Medicine, Massachusetts General Hospital, Boston, Massachusetts, USA eAfrica Centre for Health and Population Studies, Mtubatuba, South Africa.
authors.forename: Jacob
authors.initials: J
authors.lastname: Bor
authors.forename: Pascal
authors.initials: P
authors.lastname: Geldsetzer
authors.forename: Atheendar
authors.initials: A
authors.lastname: Venkataramani
authors.forename: Till
authors.initials: T
authors.lastname: Bärnighausen
mesh_terms: D015658:HIV Infections / Q000175:diagnosis* / Q000188:drug therapy* / Q000517:prevention & control; D006302:Health Services Research / Q000379:methods*; D006801:Humans; D012107:Research Design; D016896:Treatment Outcome