Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (275 page)

   Who Should Be Suspected?

   Risk factors for IAIs include prolonged labor and premature rupture of membranes, especially with fetal distress, and when fetal scalp monitors are used; nulliparity; IAI in previous pregnancy; and concurrent STI.

   Almost all women with IAI present with fever. Other signs and symptoms include abdominal pain and uterine tenderness, leukocytosis, maternal or fetal tachycardia, and foul-smelling amniotic fluid.

   Laboratory Findings

   Laboratory tests must be interpreted in the context of the clinical presentation. Individual tests have moderate negative predictive values but reasonably good positive predictive values. Increasing numbers of supportive laboratory test findings are associated with improved positive predictive value.

   Culture: Amniotic fluid cultures are the gold standard for diagnosis. Gram stain may demonstrate organisms.

   Two or three sets of blood cultures should be collected from the mother and baby after delivery, to evaluate the possibility of bacteremia or fungemia.

   Amniotic fluid findings: Analysis of fluid glucose concentration and WBC count is recommended. An elevated WBC, or positive leukocyte esterase reaction, supports diagnosis.

   Amniotic fluid glucose concentration is usually decreased. An amniotic fluid glucose concentration <5 mg/dL has a positive predictive value approximately 90%; a glucose concentration ≥20 mg/dL has a negative predictive value approximately 90%.

   Maternal CRP is not useful for predicting IAI.

   Histology: Fetal membranes and tissue and placenta should be submitted for histologic examination, as appropriate.

Suggested Readings

Broekhuizen FF, Gilman M, Hamilton PR. Amniocentesis for gram stain and culture in preterm premature rupture of the membranes.
Obstet Gynecol.
1985;66:316–321.

Gauthier DW, Meyer WJ. Comparison of gram stain, leukocyte esterase activity, and amniotic fluid glucose concentration in predicting amniotic fluid culture results in preterm premature rupture of membranes.
Am J Obstet Gynecol.
1992;1:1092–1095.

Goldenberg RL, Hauth JC, Andrews WW. Intrauterine infection and preterm delivery.
NEJM.
2000;342:1500–1507.

Hussey M, Levy E, Pombar X, et al. Evaluating rapid diagnostic tests of intra-amniotic infection: Gram stain, amniotic fluid glucose level, and amniotic fluid to serum glucose level ratio.
Am J Obstet Gynecol.
1998;179:650–656.

Kiltz RJ, Burke S, Porreco RP. Amniotic fluid glucose concentration as a marker for intra-amniotic infection.
Obstet Gynecol.
1991;78:619–622.

Romero R, Gomez R, Chaiworapongsa T, et al. The role of infection in preterm labour and delivery.
Paediat Perinat Epidemiol.
2001;15:41–56.