Types of studies

This review will include randomised controlled trials, clinical controlled trials and quasi‐experimental studies. We will include quasi‐experimental studies because of the nature of the intervention and the control which makes conducting a standard RCT difficult or impossible.

Types of participants

Participants will be males and females ≥18 years old admitted to hospitals or clinics who are treated with LMWH. Trials involving treatment with other anticoagulant drugs will not be included.

Types of interventions

Types of interventions will be the administration of subcutaneous LMWH over different, pre‐defined durations in the two arms of the study. Administration of injections lasting 20 seconds or more will be considered as intervention and when lasting less than 20 seconds will be considered as control.

Types of outcome measures

We will include studies that explored the effect of subcutaneous LMWH injection duration on pain, bruising or hematoma. Pain intensity at the injection site may be measured by any of the following scales:

a. visual analogue scale;

b. numeric rating scale;

c. descriptive scale;

d. any other pain rating scale.

Electronic searches

The Cochrane Peripheral Vascular Diseases (PVD) Group will search their Specialised Register and the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library. The PVD Group Specialised Register is maintained by the Trials Search Co‐ordinator and is constructed from weekly electronic searches of MEDLINE, EMBASE, CINAHL, AMED, and through handsearching relevant journals. The full list of the databases, journals and conference proceedings which have been searched, as well as the search strategies used are described in the Specialised Register section of the Cochrane PVD Group module in The Cochrane Library.

We will search the following databases to identify studies:

• MEDLINE

• EMBASE 

• CINAHL

• Medical Persian Web sites (Iranmedex, SID)

Both MeSH headings and free text will be used to search the databases. The search strategy we will use for MEDLINE is described in Appendix 1. This search strategy will be adjusted as appropriate to search other electronic databases.

Searching other resources

• References lists of key (marker) papers found by the electronic search to identify others studies.

• Published studies and reviews.

In addition, we will contact relevant trial authors to identify any additional studies.

There will be no restriction of language of publication.

Selection of studies

Two authors (MM, LJ) will independently assess the titles and abstracts of all relevant studies retrieved by searching to determine whether each study has the initial eligibility criteria. Another author will assess the rejected articles.The review authors will obtain full versions of the articles that meet the inclusion criteria. Two authors (MM, LJ) will assess the full papers independently to explore those that fit the inclusion criteria. Disagreements will be resolved by discussion and, if necessary, referred to a third author.

Data extraction and management

We will extract data from all included studies. A structured form will be used to extract data. Both data extraction and data entry will be performed independently by two authors (MM, LJ). Disagreements will be resolved by discussion and, if necessary, by a third author. If data are missing or difficult to extract from a paper, we will contact relevant trial/study authors for more information. We will extract the following characteristics from each paper:

• type of study/trial;

• method of randomisation;

• method of concealment of allocation;

• blinding;

• comparison of intervention and control;

• duration of intervention;

• main inclusion and exclusion criteria;

• relevant outcomes for which data were collected;

• methods of statistical analysis.

Assessment of risk of bias in included studies

Two authors (MM, LJ) will independently assess each included study. Disagreements will be resolved by discussion and, if necessary, by a third author. We will use Jadad criteria for assessing the risk of bias (Jadad 1996). If other types of studies are included, appropriate standard checklists will be used to check the risk of bias.

Data synthesis

Appropriate statistical analysis will be used according to the guidelines suggested by the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2008). Initially the data will be analysed using a narrative method. The heterogeneity among the studies will be explored by visual inspection of the forest plots, Chi‐2 test and I². If there is a substantial level of heterogeneity we will try to identify any potential sources of heterogeneity by examining individual study and subgroup characteristics. In th event that there is any substantial heterogeneity, study results will not be combined by meta‐analysis. If the level of heterogeneity allows any meta‐analysis, a random‐effects model will be used. If there is a good level of homogeneity (e.g. P > 0.2) we might be able to combine the results using a fixed‐effect method. We will explore any publication bias by using a Funnel plot.

Sensitivity analysis

When appropriate, we will perform sensitivity analysis to assess the effect of variations in outcomes used in different included studies. For example, we will perform a sensitivity analysis to explore the possible influence of the following factors on the effect size:

• by excluding unpublished studies;

• by taking account of the quality of studies;

• by excluding studies with different languages, or from different countries.

Subgroup analysis will also be used when appropriate. For example the mean intensity of pain, the diameter of bruising, and the size of haematoma will be compared among different groups (e.g. age, sex, etc.).