Comparison of Amniotic Fluid Gram Stain and Leukocyte Esterase Activity in the Prediction of Subclinical Intraamniotic Infection

Chorioamnionitis is frequently associated with prolonged rupture of membranes, prelabor rupture of membranes (PROM), preterm prelabor rupture of memebranes (PPROM), maternal urinary tract infection, prematurity and maternal fever.  Though may be absent, signs and symptoms of chorioamnionitis include fever >37.8°C, significant maternal tachycardia (>120 beats per minute), fetal tachycardia, purulent or foul-smelling amniotic fluid or vaginal discharge, maternal leukocytosis (15,000-18,000 cells/mm³) or uterine tenderness (Sherman and Otsuki 2003).

Several serologic tests can be done on the mother or tests on the amniotic fluid can confirm clinical suspicion of chorioamnionitis.  Amniotic fluid gram stain and culture is reliable in the setting of chorioamnionitis.  Detecting glucose levels in the amniotic fluid is also an indirect indicator of chorioamnionitis as glucose is consumed by the rapidly dividing bacteria.  Another indicator for infection is an elevation of cytokines.  C-reactive protein determination was found to have a sensitivity and specificity of 80% as an early predictor of subclinical chorioamnionitis (Saini et. al. 2003).  In a study done by Grable and Heine in 2003, maternal plasma levels of defensin, a neutrophil granule product, is 76% sensitive and 94% specific in predicting histologic chorioamnionitis. Other studies have related amniotic fluid glucose concentration below 5 mg/dl (Kiltz et. al. 1991), elevated matrix metalloproteinase (MMP)-9, interleukin (IL)-6, and IL-12 (Harirah et. al. 2002, McNamara 2003) as markers for subclinical chorioamnionitis.  Unfortunately, many of these markers are routinely available especially in a developing country like ours, thus the need for cheaper alternatives for early diagnosis of chorioamnionitis. http://onlinelibrary.wiley.com/doi/10.1111/j.1742-4658.2010.07919.x/abstract

            Berhman et. al. describes neonatal infections that manifested in the first week of life is usually attributable to microorganisms transmitted from mother to infant.  Epidemiologic studies have subdivided neonatal infections to two: 1) early-onset, occurring within the first 72hrs of life and is assumed to have been transmitted perinatally from the mother, and 2) late-onset, occurring between 3-7 days.  It is assumed that late-onset infections are acquired post-natally from an environmental source.  Microorganisms most commonly associated with early-onset infection include group B Streptococcus (GBS), Escherichia coli, Haemophilus influenzae, and Listeria monocytogenes.

Signs and symptoms of neonatal sepsis are often nonspecific and subtle. Behavioral abnormalities manifested by the neonate may include lethargy, hypotonia, weak cry, and poor suck. Specific organ involvement may be manifest by 1) Pulmonary - tachypnea, respiratory distress, cyanosis, hemorrhage, and/or apnea; 2) Cardiovascular - tachycardia, hypotension, cool and clammy skin, pale or mottled appearance, and/or oliguria; 3) Gastroinstestinal symptoms - abdominal distension, vomiting, diarrhea, and/or bloody stools; 4) CNS - thermal regulatory abnormalities (hypothermia or hyperthermia), behavioral abnormalities, apnea, and/or seizures; 5) Hematopoietic system - pallor, petechiae or purpura (Anderson-Berry et. al. 2006)

Between the two simple and rapid tests, gram stain of amniotic fluid was superior to leukocyte esterase activity as predictors of subclinical intraamniotic infection in terms of higher sensitivity, positive and negative predictive values.

Although leukocyte esterase activity and gram stain had positive correlation with the detection of subclinical intraamniotic infection (p value 0.012 and 0.000 respectively), results are insufficient to be a basis for decision making.  Clinical signs and symptoms are still needed for proper evaluation and management of patients.

    Among patients positive for leukocyte esterase activity and microorganisms on gram stain, it would be prudent to provide mothers with extra education to be more observant with their babies on the development of subtle signs of infection. Likewise both pediatricians and obstetricians are advised to be more vigilant in monitoring these patients to prevent morbidities