Comparison of Two Screening Methods of Virginal Group B Streptococcus Colonization in Late Pregnancy

  Objective   To compare the scanning efficiency between the traditional vaginal swab culture and Lim broth subinoculation culture using vaginal-rectal swab for group B Streptococcus (GBS) colonization in late pregnancy.

  Methods   A total of 1371 pregnant women who received prenatal care in Peking Union Medical College Hospital from December 2014 to August 2015 were enrolled in the study. Each patient got both kinds of culture in the 35th to 37th week of pregnancy. The positive rate, detection rate, and false negative rate of these two screening methods were compared and analyzed by chi-square test.

  Results   The colonization rate of vaginal GBS in late pregnancy was 8.0%. The detection rate of traditional vaginal swab culture was 41.8% with a false negative rate of 58.2%, and the detection rate of vaginal-rectal swab culture was 80.0% with a false negative rate of 20.0%. The difference in the detection rate between these two methods was statistically significant (P < 0.01).

  Conclusions   The screening efficiency of Lim broth subinoculation culture using vaginal-rectal swab for GBS colonization in late pregnancy is superior to the traditional vaginal swab culture. Combined application of both methods might improve the detection rate and avoid the missed diagnosis.