PlGF Unit Converter

Q: Is pg/mL the same as ng/L for PlGF?

Yes, exactly and always. A picogram per millilitre and a nanogram per litre are the same concentration: the prefix changes by a thousand, the volume changes by a thousand, and the two cancel. Nanograms per millilitre and micrograms per litre are likewise identical to each other and are both the pg/mL figure divided by a thousand. Every PlGF assay in current guidance reports in pg/mL.

Q: Why is there no pmol/L option for PlGF?

Because PlGF has no single molar mass to convert against. It is a homodimeric glycoprotein of the VEGF family, around 50 kDa, whose mass varies with glycosylation, and it is quantified against each manufacturer's protein calibrator rather than against a defined molecular weight. A pmol/L figure would require assuming a mass, which would present an assumption as an arithmetic conversion. Mass units are the only honest ladder here.

Q: What is a normal PlGF level?

That depends on which assay measured it, which is why this page does not print one. On the Triage PlGF test, 100 pg/mL or above is normal and 12 to 99 is abnormal; on the DELFIA Xpress PlGF 1-2-3 test, 150 pg/mL or above rules pre-eclampsia out and below 50 rules it in. A PlGF of 120 pg/mL is therefore normal on the first and indeterminate on the second. Both are recommended tests in the same national guidance. Use the threshold the laboratory that ran your sample prints beside the result.

Q: Can I compare a PlGF from one laboratory with a PlGF from another?

Not safely, even though the units convert exactly. The assays are calibrated independently and their validated cut-points differ substantially — the two PlGF-alone tests in NICE's guidance disagree by 50 pg/mL on where a rule-out sits. A serial PlGF within one laboratory on one platform is interpretable; a single value compared against a number from a different platform, a paper or a memory of a threshold is not. If the platform is not stated, the comparison is unavailable rather than approximate.

Q: Is a PlGF on its own enough, or is the ratio better?

The ratio has the evidence. PlGF falls before pre-eclampsia declares itself while sFlt-1 rises, so the ratio moves further than either component and is what the trials tested. In PROGNOSIS, 550 women with suspected pre-eclampsia, an sFlt-1:PlGF ratio of 38 or lower gave a negative predictive value of 99.3% for pre-eclampsia within the next week, with a positive predictive value of 36.7% over four weeks. That shape — strong rule-out, weak rule-in — is the shape to expect. PlGF alone is used where only a PlGF assay is available, with its own platform-specific thresholds.

Q: Does a normal PlGF exclude pre-eclampsia?

It lowers the probability substantially over the following week and does not exclude the diagnosis, and it does not replace the clinical and laboratory definition. Pre-eclampsia is defined by hypertension with proteinuria or maternal organ dysfunction, and a reassuring angiogenic result does not overrule a rising blood pressure, a rising protein-creatinine ratio, falling platelets or deranged liver enzymes. The biomarkers are rule-out tools inside a clinical assessment, not a substitute for it.

Convert placental growth factor between pg/mL, ng/L, ng/mL and µg/L — the first two are the same number. There is deliberately no reference interval on this page, because every published PlGF threshold belongs to a named assay rather than to the measurand, and the thresholds differ between manufacturers by more than any clinical judgement would.

Last updated 18 Sep 2026

PlGF converter

Mass units only

Placental growth factor

pg/mL and ng/L are numerically identical. ng/mL and µg/L are that number divided by 1,000 and are also identical to each other, so a PlGF near 0.06 has almost certainly come back in one of those two.

60pg/mLExample

PlGF 60 pg/mL at 30 weeks

The ladder, and why no molar unit appears

1 pg/mL = 1 ng/L (identical)
1 ng/mL = 1 µg/L = 1,000 pg/mL
no pmol/L is offered, and none should be

pg/mL = ng/L: a picogram in a millilitre is a nanogram in a litre. The prefix changes a thousandfold, the volume changes a thousandfold, and the two cancel, so the number does not move. Assay inserts and most reports print pg/mL
ng/mL = µg/L: the same identity one rung up, and both are the pg/mL figure divided by a thousand. A PlGF printed as 0.06 rather than 60 is on this rung, and comparing it with a published threshold without converting it first is the one mistake this ladder prevents
no molar unit: PlGF is a homodimeric glycoprotein of the VEGF family, around 50 kDa, whose mass varies with glycosylation and which is measured against an assay calibrator rather than against a molar mass. There is no single grams per mole to divide by, so a pmol/L figure here would be an assumption wearing the clothes of a conversion
what the units cannot reconcile: the platforms. Two manufacturers’ PlGF assays are not interchangeable: on one, 100 pg/mL is the boundary of a normal result; on another, the rule-out threshold is 150 pg/mL and the rule-in is 50. Converting correctly between pg/mL and ng/L does nothing about that, and the table below is the reason this page carries no reference interval

Worked example

PlGF 60 pg/mL at 30 weeks
60 pg/mL is 60 ng/L — the same number
60 ÷ 1,000 = 0.060 ng/mL, which is also 0.060 µg/L
No verdict follows from the conversion, and this page offers none: on one manufacturer's test 60 pg/mL falls in the abnormal band below 100, on another it sits between the 50 pg/mL rule-in and the 150 pg/mL rule-out
Read the number against the threshold printed on your own report, by the laboratory that measured it
If an sFlt-1 was measured on the same sample, the ratio is the more studied quantity: see the sFlt-1/PlGF ratio calculator

Four PlGF-based tests, four sets of thresholds

Read the first two rows against each other and the argument of this page is made without commentary. A PlGF of 120 pg/mL is a normal Triage result and an indeterminate DELFIA Xpress one; a PlGF of 60 pg/mL is abnormal on Triage and above the DELFIA Xpress rule-in threshold. The ratio rows say the same thing again: the same short-term rule-out decision is a ratio of 38 on the Roche assay and 50 on the PerkinElmer one, and the same rule-in decision is 85 and 110 on one, 70 and 90 on another, and a flat 85 on a third. All five are recommended tests in the same piece of national guidance, which notes that "the tests should be used according to their indications for use". That is why this page prints no reference interval: there is no number here that belongs to placental growth factor rather than to a manufacturer’s calibrator.
Test and platform	Units	Thresholds as the guidance prints them
Triage PLGF Test (Quidel)	pg/mL	"<12 pg/ml" highly abnormal; 12–99 pg/mL abnormal; "≥100 pg/ml" normal
DELFIA Xpress PLGF 1‑2‑3 (PerkinElmer)	pg/mL	"<50 pg/ml" rule in; "≥150 pg/ml" rule out
Elecsys sFlt‑1/PLGF ratio (Roche)	ratio	Rule out ≤33 and rule in 85 from 20 to 33+6 weeks; rule in 110 from 34 weeks; short-term rule out "≤38"
DELFIA Xpress sFlt‑1/PLGF ratio (PerkinElmer)	ratio	Rule in ≥70 from 20 to 33+6 weeks; ≥90 from 34 weeks; short-term rule out "50 or less"
BRAHMS sFlt‑1 Kryptor / BRAHMS PLGF plus Kryptor (Thermo Fisher)	ratio	"A ratio of more than 85 suggests pre-eclampsia"

What the measurement is, and what follows from that

The honest summary of a PlGF in isolation is that it is one half of an angiogenic imbalance and that the half is less informative than the pair. Both directions matter: placental growth factor falls before pre-eclampsia declares itself, and soluble fms-like tyrosine kinase-1 rises, so the ratio moves further and faster than either component. That is why the studied and guideline-endorsed quantity is the ratio rather than this concentration, and why the most useful thing this converter can do is get the number onto the right rung before it is handed to the sFlt-1/PlGF ratio calculator.
Property	Consequence for the number
A homodimeric glycoprotein of the VEGF family, around 50 kDa	No fixed molar mass, so no molar unit — the ladder above is mass-only by necessity, not by convention
Quantified against each manufacturer’s own protein calibrator	Absolute concentrations are platform-specific, which is what the first table demonstrates
Falls before the clinical onset of pre-eclampsia, as sFlt-1 rises	The two are usually read together as a ratio, which partly cancels calibration differences but does not remove them
Reported in pg/mL by every assay in current guidance	The ladder on this page exists mainly to catch a report in ng/mL or µg/L, where the same result reads a thousandfold smaller

A thousandfold trap, and a threshold that belongs to a machine

This page does one small thing reliably. A picogram per millilitre and a nanogram per litre are the same concentration, because the prefix and the volume each change by a factor of a thousand and cancel; a nanogram per millilitre and a microgram per litre are likewise the same as each other, and both are the pg/mL figure divided by a thousand. Every assay in current national guidance reports PlGF in pg/mL, so the practical purpose of the ladder is to catch the occasional result printed on the lower rung, where a placental growth factor of 60 pg/mL appears as 0.06 and would be compared against a published threshold to comically wrong effect.

There is no molar unit here and there should not be. PlGF is a homodimeric glycoprotein of the vascular endothelial growth factor family, around fifty kilodaltons, with a mass that varies with its glycosylation, and it is measured against each manufacturer’s protein calibrator rather than against a molar mass. There is no single grams-per-mole to divide by, so a pmol/L figure would be an assumption presented as a conversion. The test suite that builds this site enforces that rather than trusting the author, and it is right to.

There is also no reference interval, and that absence is the substance of the page rather than a gap in it. NICE’s diagnostics guidance on PlGF-based testing recommends four tests, and their thresholds do not agree. The Triage PlGF test calls a result below 12 pg/mL highly abnormal, 12 to 99 abnormal and 100 or above normal. The DELFIA Xpress PlGF 1-2-3 test rules pre-eclampsia in below 50 pg/mL and out at 150 or above. So a PlGF of 120 pg/mL is a normal result on the first and an indeterminate one on the second, and a PlGF of 60 is abnormal on the first and below the rule-in threshold on the second. These are not competing opinions about the same measurement; they are different measurements that share a name, each with its own calibrator and its own validated cut-points. Printing any one of those numbers on this page as a reference interval would teach exactly the error the page exists to prevent.

The same pattern, more sharply, applies to the ratio with soluble fms-like tyrosine kinase-1. The short-term rule-out that most clinicians know as "38" is a Roche Elecsys figure; the PerkinElmer equivalent in the same guidance is 50. The two-sided rule-in pair of 85 before 34 weeks and 110 after is also Roche’s; PerkinElmer’s are 70 and 90, and the Thermo Fisher BRAHMS Kryptor ratio uses a flat 85. A ratio of 40 is therefore above the rule-out on one platform and below it on another, with no error made by anybody. When a threshold is quoted in a meeting or a handover without the assay being named, that is the ambiguity being carried.

What a PlGF is for, then. It falls before pre-eclampsia becomes clinically apparent, while sFlt-1 rises, so the two together describe an angiogenic imbalance more sensitively than either alone — which is why the quantity with the trial evidence behind it is the ratio and not this concentration. The PROGNOSIS study of 550 women found that an sFlt-1:PlGF ratio of 38 or lower had a negative predictive value of 99.3 per cent for pre-eclampsia in the following week, against a positive predictive value of 36.7 per cent over four weeks: a good rule-out test and a weak rule-in one. Convert the number here, read it against the threshold your own laboratory printed beside it, and if an sFlt-1 was measured on the same sample take both to the sFlt-1/PlGF ratio calculator. For the laboratory definition of the syndrome itself, including the proteinuria and organ-dysfunction criteria that a biomarker does not replace, see the pre-eclampsia laboratory criteria interpreter and the urine protein to creatinine ratio calculator.

Frequently asked questions

Is pg/mL the same as ng/L for PlGF?

Yes, exactly and always. A picogram per millilitre and a nanogram per litre are the same concentration: the prefix changes by a thousand, the volume changes by a thousand, and the two cancel. Nanograms per millilitre and micrograms per litre are likewise identical to each other and are both the pg/mL figure divided by a thousand. Every PlGF assay in current guidance reports in pg/mL.

Why is there no pmol/L option for PlGF?

Because PlGF has no single molar mass to convert against. It is a homodimeric glycoprotein of the VEGF family, around 50 kDa, whose mass varies with glycosylation, and it is quantified against each manufacturer’s protein calibrator rather than against a defined molecular weight. A pmol/L figure would require assuming a mass, which would present an assumption as an arithmetic conversion. Mass units are the only honest ladder here.

What is a normal PlGF level?

That depends on which assay measured it, which is why this page does not print one. On the Triage PlGF test, 100 pg/mL or above is normal and 12 to 99 is abnormal; on the DELFIA Xpress PlGF 1-2-3 test, 150 pg/mL or above rules pre-eclampsia out and below 50 rules it in. A PlGF of 120 pg/mL is therefore normal on the first and indeterminate on the second. Both are recommended tests in the same national guidance. Use the threshold the laboratory that ran your sample prints beside the result.

Can I compare a PlGF from one laboratory with a PlGF from another?

Not safely, even though the units convert exactly. The assays are calibrated independently and their validated cut-points differ substantially — the two PlGF-alone tests in NICE’s guidance disagree by 50 pg/mL on where a rule-out sits. A serial PlGF within one laboratory on one platform is interpretable; a single value compared against a number from a different platform, a paper or a memory of a threshold is not. If the platform is not stated, the comparison is unavailable rather than approximate.

Is a PlGF on its own enough, or is the ratio better?

The ratio has the evidence. PlGF falls before pre-eclampsia declares itself while sFlt-1 rises, so the ratio moves further than either component and is what the trials tested. In PROGNOSIS, 550 women with suspected pre-eclampsia, an sFlt-1:PlGF ratio of 38 or lower gave a negative predictive value of 99.3% for pre-eclampsia within the next week, with a positive predictive value of 36.7% over four weeks. That shape — strong rule-out, weak rule-in — is the shape to expect. PlGF alone is used where only a PlGF assay is available, with its own platform-specific thresholds.

Does a normal PlGF exclude pre-eclampsia?

It lowers the probability substantially over the following week and does not exclude the diagnosis, and it does not replace the clinical and laboratory definition. Pre-eclampsia is defined by hypertension with proteinuria or maternal organ dysfunction, and a reassuring angiogenic result does not overrule a rising blood pressure, a rising protein-creatinine ratio, falling platelets or deranged liver enzymes. The biomarkers are rule-out tools inside a clinical assessment, not a substitute for it.

Related calculators

References

National Institute for Health and Care Excellence. PLGF-based testing to help diagnose suspected preterm pre-eclampsia. Diagnostics guidance DG49. Recommends the "DELFIA Xpress PLGF 1‑2‑3", "DELFIA Xpress sFlt‑1/PLGF 1‑2‑3 ratio", "Elecsys immunoassay sFlt‑1/PLGF ratio" and "Triage PLGF Test". Triage "<12 pg/ml" highly abnormal, 12–99 abnormal, "≥100 pg/ml" normal; DELFIA Xpress PlGF "<50 pg/ml" rule in and "≥150 pg/ml" rule out; Elecsys ratio rule out 33 and rule in 85 at 20–33+6 weeks, 110 from 34 weeks, short-term rule out "≤38"; DELFIA Xpress ratio rule in ≥70 and ≥90, short-term rule out "50 or less"; BRAHMS Kryptor "A ratio of more than 85 suggests pre-eclampsia". "The tests should be used according to their indications for use."
Zeisler H, Llurba E, Chantraine F, et al. Predictive value of the sFlt-1:PlGF ratio in women with suspected preeclampsia. N Engl J Med. 2016;374(1):13–22. Validation cohort of 550 women; "an sFlt-1:PlGF ratio of 38 or lower had a negative predictive value (i.e., no preeclampsia in the subsequent week) of 99.3% (95% confidence interval [CI], 97.9 to 99.9)"; positive predictive value for a ratio above 38 of 36.7%.
CalcEngines _factors.json, analyte plgf: "a ~50 kDa homodimeric glycoprotein of the VEGF family, reported as a mass concentration against an assay calibrator; pg/mL and ng/L are identical … the Roche and the Perkin-Elmer/Thermo assays are not interchangeable and the sFlt-1:PlGF ratio cut-offs are specific to the platform they were derived on."

Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.