title: Performance of RT-PCR in the detection of Streptococcus agalactiae in the anogenital tract of pregnant women.
abstract: BACKGROUND
  Infection with Group B Streptococcus (GBS) is the most frequent in the first weeks of life of a newborn. The identification of pregnant women with GBS colonization may reduce neonatal infection.
  
  
  METHODS
  This cross-sectional study evaluated the performance of real-time polymerase chain reaction (RT-PCR) to detect GBS colonization in the anogenital tract of pregnant women. Anogenital swabs were collected from 266 pregnant women from December 2010 to August 2011. GBS was detected using culture (gold standard) and RT-PCR to determine sip gene expression. The presence of DNA was confirmed using betaglobin amplification, and the guanidine technique was used for DNA extraction. When results were discordant, the test was repeated using conventional PCR. The results were evaluated to determine sensitivity, specificity, positive and negative predictive values and accuracy.
  
  
  RESULTS
  Of the 266 samples collected, 254 were adequate for analysis. Prevalence was 28.7% using the gold standard criterion and 38.2% using RT-PCR. The comparison of RT-PCR with culture revealed a sensitivity of 89% (95% CI 0.81-0.96), specificity of 82% (95% CI 0.76-0.87), positive predictive value of 67% (95% CI 0.57-0.76) and negative predictive value of 94% (95% CI 0.91-0.99).
  
  
  CONCLUSIONS
  Further studies using other DNA extraction techniques, targeting other GBS genes and using sample enhancement before RT-PCR should be conducted to determine whether the sensitivity and specificity recommended by the CDC may be reached using the same thermal cycler.
authors.affiliation: UNISUL, Universidade do Sul de Santa Catarina, Dehon Tubarão, Brazil. Otto.feurschuette@unisul.br
authors.forename: Otto May
authors.initials: OM
authors.lastname: Feuerschuette
authors.forename: Ana Claudina
authors.initials: AC
authors.lastname: Serratine
authors.forename: Maria Luiza
authors.initials: ML
authors.lastname: Bazzo
authors.forename: Toni Ricardo
authors.initials: TR
authors.lastname: Martins
authors.forename: Sheila Koetker
authors.initials: SK
authors.lastname: Silveira
authors.forename: Rosemeri Maurici
authors.initials: RM
authors.lastname: da Silva
mesh_terms: D000328:Adult; D001003:Anal Canal / Q000382:microbiology; D000942:Antigens, Bacterial / Q000235:genetics; D001431:Bacteriological Techniques; D002353:Carrier State / Q000175:diagnosis*; D003430:Cross-Sectional Studies; D004269:DNA, Bacterial / Q000032:analysis; D005260:Female; D006801:Humans; D011237:Predictive Value of Tests; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis*; D060888:Real-Time Polymerase Chain Reaction; D015203:Reproducibility of Results; D013290:Streptococcal Infections / Q000175:diagnosis*; D013292:Streptococcus agalactiae / Q000235:genetics / Q000302:isolation & purification*; D014621:Vagina / Q000382:microbiology; D055815:Young Adult
chemical_list: D000942:Antigens, Bacterial; D004269:DNA, Bacterial; C414463:SIP protein, Streptococcus group B