Meta-Analyses are Quantitative Reviews

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Human head. Coloured composite image of a magnetic resonance imaging (MRI) scan of the brain and 2D and 3D computed tomography (CT) scans of the head and neck of a 35 year old patient. Zephyr/Science Photo LIbrary/Getty Imges

What is the definition of a meta-analysis or pooled analysis?

A meta-analysis is a type of study that uses statistical techniques to analyze the combined results of a series of studies with related hypotheses that have been previously published. A meta-analysis is a type of pooled analysis uses special statistical techniques to combine the results of other studies in ways that take into account the original study's design and quality.

Another name for meta analysis is quantitative review, which distinguishes this type of study from typical review studies that look at the results of numerous studies without reanalyzing or combining their data.

Meta analysis is a useful tool in the scientist's arsenal, since it provides a quantitative, and somewhat objective, way to combine the results of various studies on the same topic. This allows scientists to try to analyze how the results of the studies, which may be very different, combine to form a more complete picture. Combining studies can also allow scientists to find out whether a small effect was significant, something that may be difficult to do in a single study that has fewer enrollees.

The biggest weakness of meta-analysis is that it relies only on pre-existing studies rather than any original data collection. This means that any flaws that consistently run through the early studies may be magnified in the meta-analysis.

Meta analysis may also be hampered by publication bias -- if there is a tendency for journals to only publish positive results (and not studies that show little to no effect), then the magnitude of an association seen in a pooled analysis may seem to be larger than it actually is.

Also Known As: quantitative review, pooled analysis

Alternate Spellings: meta analysis

A Few Examples of Meta Analyses About Sexual  Health

A 2009 meta-analysis of six studies that peripherally addressed the use of condoms to prevent genital herpes transmission found that using condoms did seem to be an effective method to reduce the sexual transmission of HSV2. Similar meta-analyses have shown that condoms are effective at reducing HIV transmission.

Some other meta-analyses looking at STD related topics have shown that:

  • Self-collected vaginal swabs can be used to test for gonorrhea and chlamydia in women (and self-collected urine can be used for home testing in men)
  • Gonorrhea is associated with an increased risk of prostate cancer
  • ART reduces HIV transmission, and works even better with condoms.
  • Mycoplasma causes significant symptoms in women, and can lead to infertility

Sources:

Giannou FK, Tsiara CG, Nikolopoulos GK, Talias M, Benetou V, Kantzanou M, Bonovas S, Hatzakis A. Condom effectiveness in reducing heterosexual HIV transmission: a systematic review and meta-analysis of studies on HIV serodiscordant couples. Expert Rev Pharmacoecon Outcomes Res. 2015 Oct 21:1-11.

Lian WQ, Luo F, Song XL, Lu YJ, Zhao SC. Gonorrhea and Prostate Cancer Incidence: An Updated Meta-Analysis of 21 Epidemiologic Studies. Med Sci Monit. 2015 Jul 1;21:1902-10. doi: 10.12659/MSM.893579.

Lis R, Rowhani-Rahbar A, Manhart LE. Mycoplasma genitalium infection and female reproductive tract disease: a meta-analysis. Clin Infect Dis. 2015 Aug 1;61(3):418-26. doi: 10.1093/cid/civ312.

Liu H, Su Y, Zhu L, Xing J, Wu J, Wang N. Effectiveness of ART and condom use for prevention of sexual HIV transmission in serodiscordant couples: a systematic review and meta-analysis. PLoS One. 2014 Nov 4;9(11):e111175. doi: 10.1371/journal.pone.0111175.

Lunny C, Taylor D, Hoang L, Wong T, Gilbert M, Lester R, Krajden M, Ogilvie G. Self-Collected versus Clinician-Collected Sampling for Chlamydia and Gonorrhea Screening: A Systemic Review and Meta-Analysis. PLoS One. 2015 Jul 13;10(7):e0132776. doi: 10.1371/journal.pone.0132776.

Martin ET, Krantz E, Gottlieb SL, Magaret AS, Langenberg A, Stanberry L, Kamb M, Wald A. A pooled analysis of the effect of condoms in preventing HSV-2 acquisition. Arch Intern Med. 2009 Jul 13;169(13):1233-40. doi: 10.1001/archinternmed.2009.177. Erratum in: Arch Intern Med. 2010 Jun
14;170(11):929.

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