Data collection. Two people (either N.H. and C.G.E.
or H.R. and C.G.E.) independently screened each abstract
according to the exclusion and inclusion criteria.
After abstract screening, we recalled relevant studies for
full-text review. On full-text review by H.R. and N.H., we
made final decisions to include or exclude studies. Bibliographies
of included studies were also hand searched
(by N.H.) for relevant studies not yet identified.