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first-trimester markers for late-onset PE

Posted: Tue Sep 09, 2008 02:13 pm
by caryn
sEng and sFlt1 serum concentrations were higher in women with subsequent preeclampsia than in controls (mean +/- SD, sEng: 5.57 +/- 1.18 ng/mL vs 5.02 +/- 1.01 ng/mL, P = .009; sFlt1: 1764 +/- 757 pg/mL vs 1537 +/- 812 pg/mL, P = .036). Sensitivities and specificities for predicting preeclampsia were 63% and 57% for sEng and 64% and 56% for sFlt1, respectively. When sEng and inhibin A were combined, the sensitivity increased to 68%, whereas the specificity was 61%...

This means that even though we know sEng and sFlt-1 are definitely preeclampsia factors, and even though they are elevated in women who develop preeclampsia, measuring them directly doesn't give us a good screening test.

Sensitivity is ability to pick up *all* the preeclamptics, and specificity is ability to pick up *only* the preeclamptics. Usually in a screening test they'll make sacrifices in specificity to improve sensitivity, because it is better not to miss sick people.

These numbers are just examples, but it often comes down to two choices:

1) monitor 40 women closely for preeclampsia even though 29 of them don't get it to avoid failing to catch one (high sensitivity, low specificity)


2) monitor 10 women closely for preeclampsia and miss one woman who does go on to develop it but whom your screening test missed (high specificity, low sensitivity)

But the values aren't really high enough here to make a good screening test. So they're looking for other markers they could measure at the same time that would improve sensitivity and specificity. Adding inhibin A makes the test both more sensitive and more specific, but not enough of either to make the screening test very good. (Coupling these tests to a uterine artery Doppler also helps.)

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