In women
> 20 weeks gestation with clinical suspicion of preeclampsia, a serum
sFlt/PlGF ratio (by Roche assay) less than 38 rules out preeclampsia for at
least 1 week.
Uncertainty of Measurement:
sFlt-1:
5%, PlGF: 5%
Requests must be made by SMOs/consultants only. See below for appropriate test indications (i.e. approval criteria). Test requests can be rejected if there are no clear clinical details/indications written on the blood request form or lacking the requesting SMO's details.
Pregnant women in >20 weeks gestation AND one of
- Systolic blood pressure >= 130 mmHg and/or diastolic blood pressure >= 80 mmHg
- Renal insufficiency, proteinuria, thrombocytopenia, liver dysfunction without
hypertension
- Symptoms suggestive of preeclampsia e.g. headache, abdominal pain, epigastric
pain or visual field disturbance
- When another alternate diagnosis is being considered e.g. SLE, underlying
renal or liver disease
- Suspicion of fetal growth restriction
- One test (sFlt-1/PlGF ratio) per week per patient only
Clinical Interpretation:
Preeclampsia (PE) is a placental disorder which can affect multisystem and can cause significant adverse effects on both mother and baby. PE affects 2%-8% of pregnancies, causing 10%-15% of direct maternal deaths globally.
Although the exact aetiology is unclear, there is good evidence showing that PE is partly due to endogenous angiogenic imbalance, leading to placental dysfunction. sFlt-1 (soluble fms-like tyrosine kinase-1) is an anti-angiogenic factor and PlGF (placental growth factor) is a proangiogenic factor. In patients with PE or those who will develop PE, there is an increase in sFlt-1 and a decrease in PlGF. The sFlt-1/PlGF ratio has shown to be clinical useful in identifying patients at risk of developing PE or predicting the related maternal or fetal outcomes.
Serum sFlt-1/PlGF ratio is most useful (predictive) in early pregnancy (i.e. 20-34 weeks of gestation), however it is still useful in late pregnancy (i.e. 34 or more weeks of gestation).
Based on host of large clinical studies, a threshold of 38 is the most well-established and well validated cut-off, using Roche Cobas assays. In patients with >20 weeks gestation and have symptoms of having pre-eclampsia, a serum sFlt-1/PlGF ratio of <38 rules out PE for at least 1 week with >99% negative predictive value.[ 1 ]
In addition, many studies have evaluated further clinical cut offs, to classify those at high risk. Considered at high risk if serum sFlt-1/PlGF ratio greater than 85 for those in gestational age 20-34 weeks, and greater than 110 for those in gestational age >34 weeks. If the ratio is in between, the risk is considered intermediate. [ 2 , 3 ]
|
Serum Sflt-1/PlGF ratio |
GA: 20-34 weeks |
GA: >34 weeks |
|
>110 |
High risk - highly suggestive of PE or having a PE related adverse outcomes. |
High risk - highly suggestive of PE or having a PE related adverse outcomes. |
|
>85-110 |
Intermediate risk |
|
|
38-85 |
Intermediate risk |
|
|
<38 |
Low risk, very unlikely to develop PE for at least 1 week or can be considered at low risk for having PE related adverse outcomes |
Low risk, very unlikely to develop PE for at least 1 week or can be considered at low risk for having PE related adverse outcomes |
1. Zeisler, H., et al., Predictive Value of the sFlt-1:PlGF Ratio in Women with Suspected Preeclampsia. N Engl J Med, 2016. 374(1): p. 13-22
2. Flint, E.J., et al., The role of angiogenic factors in the management of preeclampsia. Acta Obstet Gynecol Scand, 2019. 98(6): p. 700-707.
3. Verlohren, S. and L.A. Droge, The diagnostic value of angiogenic and antiangiogenic factors in differential diagnosis of preeclampsia. Am J Obstet Gynecol, 2020.
Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.
If the query concerns a specific patient please include the NHI number in your email.
If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).
Individual chemical pathologists may be contacted but will not be available at all times.
After-hours : contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.
Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402
Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052
Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427
Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427
Dr Sakunthala Jayasinghe: Sakunthala@adhb.govt.nz ext. 23427