Based on this study (PARROT) NHS England is rolling PlGF testing nationally, to all pregnant women with suspected pre-eclampsia
What did the stepped wedge cluster trial do?
Population - women with suspected pre-eclampsia
Intervention - PlGF test results revealed. (see supplementary appendix).
If PlGF less than 12 pg/ml then clinicians are asked to admit and measure blood pressure 4 times a day, and do all the tests needed to diagnose pre-eclampsia, and ultrasound
If PlGF more than 100 pg/ml then clinicians are asked to send the patient home, and only measure blood pressure once a week.
12-200 pg/ml twice a week blood pressure, ultrasound, and blood tests for pre-eclampsia
Control: Usual care where for suspected pre-eclampsia (blinded to PlGF results) will not be checking blood pressure that often, may be twice a week or doing ultrasound for fetal growth
Outcome: Time to diagnose pre-eclampsia (which could be high blood pressure with proteinuria or abnormal fetal growth or abnormal blood tests)
So by virtue of knowing the test results, clinicians monitor intensely in test positive patients, and are more likely to diagnose pre-eclampsia early; whereas usual care group only monitors less frequently, does not do scans (a criteria for diagnosing pre-eclampsia), and hence is not likely to diagnose early.
- Sample size calculation:
for 50% reduction in mean time to diagnosis of pre-eclampsia.
For the actual RCT result,
Time to diagnosis of pre-eclampsia
control median 4.1 days (0.5-9.2)
intervention median 2.2 days (0.8-14.7)
The primary outcome is reported as time ratio 0·36 (95% CI 0·15–0·87; p=0·027).
There is overlapping CI in median between the two groups.
Secondary outcome of severe maternal morbidity 22 [4%] vs 24 [5%] events; aOR 0·32, 95% CI 0·11 to 0·96; p=0·043, and highlighted as benefit in abstract
Look forward to discussion on above in this forum.