Evaluation of polymerase chain reaction for group B streptococcus detection using an improved culture method.
OBJECTIVE
The administration of antibiotic prophylaxis to laboring women who harbor Group B streptococci (GBS) depends on identification of carriers. We sought to evaluate the diagnostic accuracy of real-time polymerase chain reaction (PCR) for detection of GBS using a more stringent culture method.


METHODS
Two swabs were used simultaneously to obtain rectovaginal GBS samples from consenting women. One swab was analyzed using a stringent, validated culture technology, which included direct plating onto selective agar and inoculation of a selective broth. The other swab was used for a commercial real-time PCR assay, which uses amplification to detect the presence of the cfb gene sequence of GBS DNA. We calculated the assay accuracy using sensitivity and specificity.


RESULTS
A total of 233 samples were available. Both the culture and PCR methods were positive for 59 and negative for 157 patients. The culture method was positive and PCR was negative in 9 patients. The culture was negative and the PCR positive for 8 patients. The sensitivity of the PCR assay was 86.8% and specificity was 95.2%. The positive predictive value was 88.1% and the negative predictive value was 94.6%.


CONCLUSIONS
Although a rapid PCR assay may be useful to determine GBS status in the urgent intrapartum setting, the false-negative rate of 13.2% for the real-time PCR assay prohibits its use for standard GBS screening in the office.
Atkins
Kristin L
KL
Department of Obstetrics & Gynecology, Washington University in St. Louis, Saint Louis, Missouri 63110, USA. atkinsk@wustl.edu
Atkinson
Robyn M
RM
Shanks
Anthony
A
Parvin
Curtis A
CA
Dunne
W Michael
WM
Gross
Gilad
G
D000293:Adolescent; D000328:Adult; D002353:Carrier State / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology; D015169:Colony Count, Microbial; D003470:Culture Media; D004269:DNA, Bacterial / Q000032:analysis*; D005188:False Negative Reactions; D005260:Female; D005784:Gene Amplification; D006801:Humans; D008403:Mass Screening; D016133:Polymerase Chain Reaction / Q000379:methods*; D011237:Predictive Value of Tests; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis* / Q000453:epidemiology / Q000382:microbiology; D012007:Rectum / Q000382:microbiology; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013290:Streptococcal Infections / Q000175:diagnosis* / Q000453:epidemiology / Q000382:microbiology; D013292:Streptococcus agalactiae / Q000235:genetics / Q000302:isolation & purification*; D014621:Vagina / Q000382:microbiology
D003470:Culture Media; D004269:DNA, Bacterial