Use of the Serum Bacterial Antigen Test for the Detection of Group B Streptococcal Neonatal Sepsis

Mitchell Goldstein; Linda Yang; Gilbert Martin; Mita Shah; Sue Bloom; Clark Ochikubo; Perpetua Lawas-Alejo; Bruce Sindel; Gilbert Furman

Disclosures

NAINR. 2015;15(1):28-32. 

In This Article

Abstract and Introduction

Abstract

The Revised Guidelines from the Centers for Disease Control for the Prevention of Perinatal Group B Streptococcal Disease were presented in the Morbidity and Mortality Weekly Report. An algorithm for evaluation of Group B Streptococcal sepsis (GBS) included CBC and differential, blood culture, possible chest x-ray, and lumbar puncture when signs of sepsis were present. The serum bacterial antigen was not mentioned in the recommendations although its clinical use for GBS evaluation has continued. We sought to determine if routine use of Group B Streptococcal Serum Antigen screening was indicated. According to hospital practice, serum bacterial antigens were drawn along with blood cultures in evaluation of sepsis for patients up to 2 months of age. Use of serum bacterial antigen testing using the BD Directigen Combo test was analyzed retrospectively over a five year period. Predictive value, sensitivity, and specificity of the analysis were studied relative to presence of a positive blood culture result. Over a five year period (2001–2005), 3336 serum bacterial antigens were performed. During that time, there were 23 positives (0.69%) for GBS. There were 3313 negatives (99%). There were 11 cases where the bacterial antigen predicted the Group B neonatal sepsis. There were 12 cases where the bacterial antigen test was positive for GBS; however, the blood cultures had no growth. In two cases, the antigen test was positive for GBS with a positive blood culture for a different bacterium: one blood culture grew Bacillus species; and the other, coagulase negative Staphylococcus. During 2005, the NICU had no positive blood cultures for GBS, and there were only two other cases hospital-wide where the bacterial antigen test predicted a positive blood culture for GBS. Although sensitivity, specificity, and negative predictive value were 99%–100%, the positive predictive value was 48% with a disease prevalence of 0.33%. Continued evaluation of Group B Streptococcal Antigen would not result in an identifiable risk reduction and is not justifiable for routine screening.

Introduction

Despite the great accomplishments since the institution of effective prophylaxis, GBS remains the number one cause of infant morbidity and mortality in the United States.[1–6] Revised Guidelines for the Prevention of Perinatal Group B Streptococcal (GBS) Disease were published in the Morbidity and Mortality Weekly Report (MMWR) on November 19, 2010.[7] These 2010 guidelines were developed using an evidence-based approach in collaboration with a number of different professional associations including the American Academy of Family Physicians (AAFP), the American Academy of Pediatrics (AAP), the American College of Nurse-Midwives (ACNM), the American College of Obstetricians and Gynecologists (ACOG), and the American Society for Microbiology (ASM). An algorithm for evaluation of Group B Streptococcal sepsis (GBS) was presented. This evaluation included a CBC with differential, blood culture, possible chest x-ray, and lumbar puncture when signs of sepsis were present. These changes were subsequently incorporated into the Red Book recommendations.[7–9]

In our practice, the testing for Group B Streptococcal bacterial antigen was not intended to be used as a substitute for bacterial culture in the diagnosis of group B streptococcal septicemia and/or meningitis.[10] A positive or negative group B streptococcal result only reflected whether or not there is group B streptococcal antigen present at sufficient concentration in the sample measured and is not diagnostic for group B streptococcal disease.[11,12] Although the serum bacterial antigen was not specifically mentioned in the recommendations for the evaluation of newborn sepsis, its clinical use for GBS evaluation has continued in a number of venues.[8] Very little information is available regarding the use of serum bacterial antigens in determination of neonatal sepsis.

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