Search strategy and evidence selection

Search strategy and evidence selection

Search strategy

The search strategy was designed to identify evidence on the clinical and cost effectiveness of the Alair BT System in adults with severe asthma which remains uncontrolled despite the use of inhaled steroids and long‑acting beta agonists.

The strategy was developed in MEDLINE (Ovid interface). The strategy was devised using a combination of subject indexing terms and free text search terms in the title, abstract and keyword heading word fields. The search terms were identified through discussion within the research team, scanning background literature, browsing database thesauri and use of the PubMed PubReminer tool. The strategy reflected the nature of the MIB assessments as rapid evidence reviews, with a relatively pragmatic approach being taken.

The main structure of the draft strategy comprised 2 concepts:

  • Severe persistent asthma in adults

  • BT.

The search concepts were combined as follows: severe persistent asthma in adults AND BT.

The strategy also used 3 stand‑alone lines which included the asthma subject heading combined with the surgery subheading, the device name, and the previous manufacturer name. These lines were designed to retrieve any studies that may have been missed by the 2 concept approach.

The strategy excluded animal studies using a standard algorithm. Non‑English language publications were also excluded from the search results. The search was restricted to studies published from 2006 to date. This date was identified by the research team as the earliest date from which relevant studies on the device would be published.

The performance of the draft Ovid MEDLINE strategy was assessed by checking retrieval of the 9 known, relevant studies identified by the research team at project start. The draft strategy successfully retrieved all 9 of the studies which were included in Ovid MEDLINE.

The final Ovid MEDLINE strategy was translated appropriately for the other databases searched. The PubMed search was limited to records not fully indexed for MEDLINE. Reflecting the scope of MIBs, records indexed as conference‑related publication types (conference abstract, conference paper, conference proceeding, conference review) were excluded from the Embase search.

The following databases were searched:

  • Cochrane Central Register of Controlled Trials (Cochrane Library, Wiley)

  • Cochrane Database of Systematic Reviews (Cochrane Library, Wiley)

  • Database of Abstracts of Reviews of Effects (Cochrane Library, Wiley)

  • Embase (Ovid SP)

  • Health Technology Assessment Database (Cochrane Library, Wiley)

  • MEDLINE and MEDLINE in Process (Ovid SP)

  • NHS Economic Evaluation Database (Cochrane Library, Wiley)

  • PubMed.

Evidence selection

A total of 561 records were retrieved from the literature search. After de‑duplication, 395 records remained. Two reviewers independently sifted these records and excluded 374 based on the following exclusion criteria:

  • articles of poor relevance against the search terms

  • publication types that are out of the project scope

  • non‑English language studies

  • conference abstracts

  • review protocols

  • articles in which neither the abstract nor the full text is freely available online.

Full records were retrieved for the remaining 21 papers, and a second sift was undertaken. Papers were excluded at this stage if they were not randomised controlled trials, systematic reviews of randomised controlled trials or economic evaluations of BT; did not address the population, intervention, comparator and outcomes needed to inform the review; or failed quality assessment. The second sift was also undertaken independently by 2 reviewers. Following the second sift 10 papers were excluded (systematic reviews: Calhoun 2015, Singh 2015, Wilhelm 2015, CADTH 2014, NIHR 2012, Hayes 2012, Hayes 2011, Hayes 2010; economic analyses: Cangelosi 2015 and Menzella 2014.)

The remaining 11 papers comprised 2 systematic reviews and meta‑analyses of RCT data (Torrego et al. [2014], Wu et al. [2011]), 1 economic analysis (Zein et al. [2015]), 3 RCTs (Cox et al. [2007; AIR trial], Pavord et al. [2007; RISA trial] and Castro et al. [2010; AIR2 trial]) with their 3 follow‑up studies (reported in 4 publications: Thomson et al. [2011], Pavord et al. [2013], Castro et al. [2011] and Wechsler et al. [2013]) and one further systematic review that reported data only from intervention group patients (not controls) that compared data from the 5‑year follow‑up with that from 1 year after thermoplasty (Zhou et al. 2015). Synthesised evidence from the systematic review was used when appropriate. The underlying RCTs and follow‑up studies were not described on a study‑by‑study basis as they were included in the systematic reviews.

The last paper (Zafari et al. 2016) was published and identified after the search date.