{"id":93,"date":"2021-05-22T23:30:54","date_gmt":"2021-05-23T03:30:54","guid":{"rendered":"https:\/\/pressbooks.bccampus.ca\/rickyturgeon\/?post_type=chapter&p=93"},"modified":"2022-01-12T23:28:37","modified_gmt":"2022-01-13T04:28:37","slug":"search","status":"publish","type":"chapter","link":"https:\/\/pressbooks.bccampus.ca\/rickyturgeon\/chapter\/search\/","title":{"raw":"Search","rendered":"Search"},"content":{"raw":"A comprehensive search is at the core of all [pb_glossary id=\"1099\"]systematic reviews[\/pb_glossary], and is essential to ensure that all relevant trials were included. A search that is not sufficiently thorough will be more vulnerable to [pb_glossary id=\"102\"]publication bias[\/pb_glossary]. In the case of [pb_glossary id=\"102\"]publication bias[\/pb_glossary] \"an ounce of prevention is worth a pound of cure\" since the tools available to identify and adjust for [pb_glossary id=\"102\"]publication bias[\/pb_glossary] are insensitive and cannot discriminate between [pb_glossary id=\"102\"]publication bias[\/pb_glossary] and alternative causes for [pb_glossary id=\"604\"]small-study effects[\/pb_glossary]. Other considerations (such as when the search was last completed) are also necessary to ensure the search is sufficiently complete.\r\n

Checklist Questions<\/h1>\r\n\r\n\r\n\r\n\r\n\r\n\r\n
Were a reasonable number of relevant databases searched?<\/td>\r\n<\/tr>\r\n
When was the search conducted? Is it likely there have been subsequent publications that may alter the results?<\/td>\r\n<\/tr>\r\n
Was a sufficient effort made to find unpublished studies (or unreported results of published studies)?<\/td>\r\n<\/tr>\r\n
Were sources of additional published\/unpublished data sought out?<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\n

Databases of published literature:<\/span><\/span> Were a reasonable number of relevant databases searched?<\/span><\/span><\/h1>\r\nIt is important to search multiple databases to maximize the identification of all relevant studies, as no single database includes all studies. One study (Royle P et al.<\/a>) compared three major databases to a set of relevant studies established by searching twenty-six additional databases:<\/span><\/span>\r\n\r\n\r\n\r\n\r\n\r\n\r\n
Table 11. Proportion of relevant trials identified by different databases.<\/caption>\r\n
Database<\/strong><\/td>\r\nProportion of relevant trials identified<\/strong><\/td>\r\n<\/tr>\r\n
MEDLINE<\/td>\r\n69%<\/td>\r\n<\/tr>\r\n
EMBASE<\/td>\r\n65%<\/td>\r\n<\/tr>\r\n
CENTRAL<\/td>\r\n79%<\/td>\r\n<\/tr>\r\n
Combining all three<\/td>\r\n97%<\/td>\r\n<\/tr>\r\n<\/tbody>\r\n<\/table>\r\nThe optimal selection of which (and how many) databases to search will depend on the discipline, topic area, and type of intervention. For example, studies evaluating nursing and physiotherapy interventions should at minimum include CINAHL<\/a> and PEDro<\/a>, respectively. A good rule-of-thumb is to search MEDLINE and at least 1-2 other topic-specific databases (e.g. EMBASE and CENTRAL for pharmacotherapy studies).<\/span><\/span>\r\n

Timeframe: When was the search conducted? Is it likely there have been subsequent publications that may alter the results?<\/h1>\r\nThere are no strict rules as to how long is too long before a review becomes outdated, as this largely depends on the rate of evidence generation in a given field or topic area. It is important to consider the rate at which new publications are being added to the literature (i.e. considering if it is a \"hot\" topic) and whether the results would likely be sensitive to new publications (i.e. a [pb_glossary id=\"1101\"]meta-analysis[\/pb_glossary] with low-to-moderate certainty). If there are already several large high-quality trials showing consistent results it is less likely that any new literature would substantially change results.\r\n
\"Hot\" topic: A living [pb_glossary id=\"1101\"]meta-analysis[\/pb_glossary] (i.e. a [pb_glossary id=\"1101\"]meta-analysis[\/pb_glossary] that is actively updated with new evidence) (Siemieniuk RA et al.<\/a>) of drug treatments for COVID-19 illustrates an instance of rapidly changing evidence. The first version, published July 2020, included 32 [pb_glossary id=\"704\"]RCTs[\/pb_glossary] and evaluated 17 therapies. The fourth version, published in March 2021, included 196 trials and evaluated 27 therapies. Under such circumstances, [pb_glossary id=\"1101\"]meta-analyses[\/pb_glossary] become quickly outdated.<\/em><\/div>\r\n
\"Cold\" topic: The evidence surrounding the cardiovascular risk associated with rosiglitazone has changed minimally for over a decade. [pb_glossary id=\"1101\"]Meta-analyses[\/pb_glossary] from 2007 and 2010 (Nissen SE et al. 2007, 2010<\/a>) demonstrated increases in the risk of myocardial infarction with rosiglitazone. Both reviews had large patient sample sizes (27,847 and 35, 531 respectively), a factor which weighed in favor of their persisting relevance. As such, the evidence on this topic has remained largely unchanged since those reviews.<\/em><\/div>\r\n

Grey literature:<\/span><\/span> Was a sufficient effort made to find unpublished studies (or unreported results of published studies)?<\/span><\/span><\/h1>\r\n
\r\n\r\nA thorough search of unpublished literature aims to minimize the effects of [pb_glossary id=\"102\"]publication bias[\/pb_glossary].\r\n
\r\n\r\nE.g. In a [pb_glossary id=\"1101\"]meta-analysis[\/pb_glossary] (Siu JT et al.<\/a>) of N-acetylcysteine for non-acetaminophen-related acute liver failure the authors searched all of:<\/em>\r\n