U.S. Preventive Services Task Force (*)
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Update of the 2001 U.S. Preventive Services Task Force (USPSTF) recommendation on screening for bacterial vaginosis in pregnancy.
The USPSTF weighed the benefits and harms of screening for bacterial vaginosis in pregnancy by identifying new evidence addressing previously identified gaps from the 2001 USPSTF recommendation. Published literature on this topic was identified by using MEDLINE, Cochrane Library databases, the Database of Abstracts of Reviews of Effects, reference lists, and consultation with experts and was systematically reviewed. When data allowed, a series of meta-analyses (using new and 2001 report data) was done to estimate the pooled effect of treatment on preterm delivery (<37 weeks, <34 weeks, or <32 weeks) and on low birthweight and preterm, premature rupture of membranes.
Do not screen for bacterial vaginosis in pregnant women at low risk for preterm delivery. (D recommendation)
Current evidence is insufficient to assess the balance of benefits and harms of screening for bacterial vaginosis in pregnant women at high risk for preterm delivery. (I statement)
Screening for bacterial vaginosis in pregnancy to prevent preterm delivery: clinical summary of a U.S. Preventive Services Task Force Recommendation.
For a summary of the evidence systematically reviewed in making these recommendations, the full recommendation statement, and supporting documents, go to www.preventiveservices.ahrq.gov. *The Centers for Disease Control and Prevention recommends 250 mg oral metronidazole 3 times daily for 7 days as the treatment of bacterial vaginosis in pregnancy.
Table 1. What the U.S. Preventive Services Task Force Grades Mean and Suggestions for Practice*
Table 2. U.S. Preventive Services Task Force Levels of Certainty Regarding Net Benefit
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Emilia H. Koumans
Division of STD Prevention, Centers for Disease Control and Prevention
September 11, 2009
Were inclusion criteria for the USPSTF review on BV treatment during pregnancy consistently applied?
In their update and review "Evidence on the benefits and harms of screening and treating pregnant women who are asymptomatic for bacterial vaginosis: an update review for the U.S. Preventive Services Task Force" (1), Dr. Nygren and colleagues reviewed the English-language literature using a variety of methods to identify randomized trials with pregnancy outcome data in women who were asymptomatic for bacterial vaginosis (2000- 2007). In their analysis of 14 trials, they found insufficient evidence to recommend screening for high risk women, and no benefit for average risk women or low risk women. They recommended that low risk women not be screened.
The inclusion criteria for pregnant women, the criteria used to define bacterial vaginosis, gestational age at testing and treatment, and therapy provided varied widely between studies. Dr. Nygren and colleagues state that inclusion criteria for the meta-analysis were trials that evaluated screening, treatment, pregnancy outcomes, or adverse effects for asymptomatic pregnant women with bacterial vaginosis. However, it is unclear whether they were consistently applied. For example, Odendaal et al. (2) did not report on symptoms, whereas the other included trials did. Of the 14 trials, only two used Nugent's (3) Gram stain score of 7-10 to define BV (4, 5). Other trials used a variety of combinations of clinical and Gram stain criteria, and one trial used Nugent's Gram stain score of 7 -10 (BV) and abnormal flora (score 4-6) (6). Some trials found a benefit (6), and some did not (4).
Ugwumadu et al. reported the results of a double-blinded, randomized, placebo-controlled trial of oral clindamycin for the treatment of bacterial vaginosis (Nugent's score of 7-10) or abnormal vaginal (score of 4-6) flora by Gram stain among asymptomatic women in the Lancet in 2003 (7). This trial found that treatment significantly reduced spontaneous preterm delivery (5% treatment vs 12% placebo) and late miscarriage (1% treatment vs 4% placebo). However, it was not included in the review by Nygren et al.
In Figure 2 of the US Preventative Services Task Force review, the authors provide the reasons for excluding studies from the meta-analyses, but do not provide references for the 13 excluded trials. None of the reasons appears to apply to the trial by Ugwumadu and colleagues; it is not clear why this was not included.
We could not find the cited Appendix or Appendix figure at www.annals.org to review the methodology for calculating the estimates of benefits and harms of screening and treatment. We wonder how the figures would change if the results of the Uguwumadu trial were included and the Odendaal trial excluded.
1. Nygren P, Fu R, Freeman M, Bougatsos C, Klebanoff M, Guise JM. Evidence on the benefits and harms of screening and treating pregnant women who are asymptomatic for bacterial vaginosis: an update review for the U.S. Preventive Services Task Force. Ann of Int Med 2008; 148(3):220- 33.
2. Odendaal HJ, Popov I, Schoeman J, Smith M, Grove D. Preterm labour --is bacterial vaginosis involved? S Afr Med J 2002; 92(3):231-4.
3. Nugent RP, Krohn MA, Hillier SL. Reliability of diagnosing bacterial vaginosis is improved by a standardized method of gram stain interpretation. J Clin Micro 1991; 29(2):297"“301.
4. Guaschino S, Ricci E, Franchi M, Frate GD, Tibaldi C, Santo DD, Ghezzi F, Benedetto C, Seta FD, Parazzini F. Treatment of asymptomatic bacterial vaginosis to prevent pre-term delivery: a randomised trial. European Journal of Obstetrics, Gynecology, & Reproductive Biology 2003;110(2):149-52.
5. Kiss H, Petricevic L, Husslein P. Prospective randomized controlled trial of an infection screening programme to reduce the rate of preterm delivery. BMJ 2004;329:371-376.
6. Lamont RF, Duncan SLB, Mandal D, Bassett P. Intravaginal clindamycin to reduce preterm birth in women with abnormal genital tract flora. Obstet Gyncol 2003;101:516-522.
7. Ugwumadu A, Manyonda I, Reid F, Hay P. Effect of early oral clindamycin on late miscarriage and preterm delivery in asymptomatic women with abnormal vaginal flora and bacterial vaginosis: a randomized controlled trial. Lancet 2003;361:983-988.
U.S. Preventive Services Task Force. Screening for Bacterial Vaginosis in Pregnancy to Prevent Preterm Delivery: U.S. Preventive Services Task Force Recommendation Statement. Ann Intern Med. 2008;148:214-219. doi: 10.7326/0003-4819-148-3-200802050-00007
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Published: Ann Intern Med. 2008;148(3):214-219.
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