Lactate Dehydrogenase (LDH) Isoform Activity in the Vaginal "Pool"

September 12, 2007

SMFM 27th Annual Meeting 2007

view the interview video: Elevated LDH Levels in PPROM


Objective: Intra-amniotic infection is characterized by an increase in the total amniotic fluid LDH activity and a specific upregulation of LDH isoforms-3, -4 and -5. We sought to determine the utility of vaginal amniotic fluid (vAF) total LDH activity and its specific isoform profile in predicting infection in women with PPROM.

Study Design: 49 Consecutive women (GA=29.5 ± -0.5 wks) with PPROM underwent vaginal "pool" sample collection followed by amniocentesis (aAF). aAF was cultured for acrobic, anaerobic, Mycoplasma, and Ureaplasma species. Women were stratified into 2 groups: (i) positive amniotic fluid cultures (+AFC, n=22) and (ii) negative amniotic fluid cultures (-AFC, n=27). In paired aAF-vAF samples the total LDH activity was determined by a kinetic UV spectrophotometric assay. The LDH isoform activity was investigated using isoelectric focusing in agarose gels.

Results: 1) In women with -AFC, the total LDH activity was higher in vAF compared to aAF (median [range] vAF:639.6 [45.8-1,368.0] vs. aAF: 177.4 [47.5-2,217.2] U/L, p<0.001). This increase was attributed to a selective upregulation of LDH isoforms -4, and -5 (p<0.05); 2) In patients with +AFC, the total LDH activity was increased in both aAF and vAF, though to a greater extent in the vaginal "pool" samples (vAF: 1,312.5 [157.4-2,739.3] vs. aAF: 414.7 [74.9-2569.9] U/L, p<0.001). The increase in total LDH activity in vAF was attributed to the upregulation of LDH isoforms -1, -2, -3 and -4; 3) The vAF total LDH activity ≥ 1000 U/L had a sensitivity, specificity, PPV and NPV of 68%, 93%, 88% and 78% respectively, for diagnosing +AFC; 4) The accuracy of the vAF LDH activity in diagnosing a +AFC was similar to that of the aAF (vAF; 82% vs. aAF: 73%, p=0.417). The test performance was independent of the rupture-to-amniocentesis interval or GBS colonization.

Conclusion: vAF total LDH activity can accurately diagnose intra-amniotic infection. The increase in total LDH activity in vAF in response to intra-amniotic infection is due to an upregulation of a different panel of LDH isoenzymes compared to that in aAF.


0002-9378/$ - see front matter


American Journal of Obstetrics and Gynecology

Volume 195, Issue 6, Supplement S (December 2006)