Presepsin Unit Converter
Presepsin Unit Converter
pg/mL and ng/L are the same number for presepsin. The molar conversion is not offered, because the 13 kDa its manufacturer quotes is a gel mobility and a 64-residue peptide weighs about half that.
Presepsin converter
pg/mL = ng/LPresepsin 320 pg/mL
Units, and the molar conversion this page does not offer
1 pg/mL = 10⁻¹² g ÷ 10⁻³ L = 10⁻⁹ g/L = 1 ng/L
ng/mL = pg/mL ÷ 1,000
- pg/mL and ng/L
- the same number. A picogram per millilitre is a nanogram per litre, because the thousandfold step down in mass is cancelled by the thousandfold step up in volume. Every published presepsin figure is in one of these two
- ng/mL
- a thousandth of the pg/mL figure, used in some research reports. A presepsin of 320 pg/mL is 0.32 ng/mL, which looks like a different measurement if the unit is missed
- no pmol/L
- deliberate. Presepsin is soluble CD14 subtype, sCD14-ST, which its manufacturer defines as “the 13 KDa (64 amino acids) N terminal fragment of soluble form of CD14”. Those two figures cannot both be a molar mass: 64 residues weigh about 7 kDa at the mean residue mass of roughly 110 Da that every peptide obeys, and 13 kDa would need a mean residue mass no amino acid reaches
- why the two differ
- the 13 kDa is an apparent mass — where the fragment runs on gel electrophoresis — and CD14 carries an N-glycosylation site at Asn37, inside the fragment. A glycosylated peptide runs heavier than its backbone. Neither figure is wrong; they measure different things
Worked example
Presepsin 320 pg/mL
320 pg/mL = 320 ng/L — identical numbers, no arithmetic
320 ÷ 1,000 = 0.32 ng/mL
Back again: 0.32 × 1,000 = 320 pg/mL, the round trip the grid above performs
The published reference interval of 55–184 pg/mL is 0.055–0.184 ng/mL
The five published sepsis cut-offs — 317, 415, 600, 600 and 729 pg/mL — are 0.317 to 0.729 ng/mL
So 320 pg/mL is above the reference interval, just above the lowest published cut-off and well below the highest: the ambiguous band, and the reason this page prints all five rather than one
Published presepsin figures, and how far apart the cut-offs are
| Figure | pg/mL (ng/L) | ng/mL | Source |
|---|---|---|---|
| Reference interval, apparently healthy adults | 55 – 184 | 0.055 – 0.184 | Giavarina and Carta 2015, PATHFAST assay |
| Sepsis cut-off | 317 | 0.317 | Liu et al, as cited by Giavarina 2015 |
| Sepsis cut-off | 415 | 0.415 | Shozushima et al, as cited by Giavarina 2015 |
| Sepsis cut-off | 600 | 0.600 | Endo et al and Ulla et al, as cited by Giavarina 2015 |
| Sepsis cut-off | 729 | 0.729 | Romualdo et al, as cited by Giavarina 2015 |
| Assay measuring range | 2.98 – 20,000 | 0.003 – 20 | Tosoh ST AIA-PACK Presepsin |
The two masses quoted for presepsin, and why neither is a molar mass
| Figure | Where it comes from | What it actually is |
|---|---|---|
| 13 kDa | Tosoh’s own description of the ST AIA-PACK Presepsin measurand | an apparent mass on electrophoresis, for a glycosylated fragment |
| About 7 kDa | 64 residues at the usual mean residue mass of roughly 110 Da | the peptide backbone, with no glycan |
| 40,076 Da | UniProt P08571, the whole CD14 precursor | the parent protein, of which presepsin is a 64-residue piece |
A fragment of a receptor, measured two hours before anything else moves
Presepsin is a piece of CD14, the receptor that presents bacterial lipopolysaccharide to Toll-like receptor 4 on monocytes and macrophages. When that receptor engages an endotoxin-LBP complex, CD14 is shed from the cell surface and cleaved — by cathepsin D among others — and the 64-residue N-terminal fragment circulates as soluble CD14 subtype, sCD14-ST. Measuring it is measuring the act of recognition itself, upstream of the cytokine cascade, which is why it moves so early: presepsin rises within about two hours of a bacterial stimulus, against three to six for procalcitonin and considerably longer for C-reactive protein.
Two things follow. First, presepsin marks bacterial recognition rather than inflammation in general, which is a different claim from procalcitonin’s and is the basis of the interest in it; its upstream partner, lipopolysaccharide binding protein, has its own page and units. Second, it is cleared renally, so impaired kidney function raises it independently of infection — a confounder that matters a great deal in exactly the population in which sepsis is suspected.
The reference interval is narrow and reasonably well established: 55 to 184 pg/mL in apparently healthy adults on a chemiluminescent enzyme immunoassay. The decision threshold is not. The same review lists five published sepsis cut-offs — 317, 415, 600, 600 and 729 pg/mL — a 2.3-fold spread with no agreed value among them. A presepsin of 500 pg/mL is therefore raised, above two of the five and below the other three, and no unit conversion resolves that. This page prints all five rather than presenting an open question as settled.
The units are simple and the one genuine subtlety is what is absent. pg/mL and ng/L are the same number; ng/mL is a thousandth of it, which is the only place a reader is likely to be caught out. There is no pmol/L column, and that is a decision rather than an omission — see the table above for the two incompatible masses quoted for this measurand. Procalcitonin remains the biomarker with guideline-grade thresholds, and Sepsis-3 defines sepsis without reference to any biomarker at all. Intervals and thresholds are method- and laboratory-dependent, and your own report’s interval, for the assay that produced the result, takes precedence. This supports a clinician’s judgement rather than replacing it: it is arithmetic on the figures entered, and knows nothing about the patient.
Frequently asked questions
Is pg/mL the same as ng/L for presepsin?
Yes — numerically identical, so 320 pg/mL and 320 ng/L mean exactly the same thing. ng/mL is a thousandth of that figure, so the same result is 0.32 ng/mL, and that is the conversion most likely to be missed.
What is the normal range for presepsin?
55 to 184 pg/mL in apparently healthy adults, measured on a chemiluminescent enzyme immunoassay. That is a single published interval from one platform, and presepsin values are not transferable between analysers, so your own laboratory’s interval takes precedence.
Why is there no pmol/L conversion for presepsin?
Because the measurand has no agreed molar mass. Its manufacturer defines presepsin as a 13 kDa, 64-amino-acid fragment of soluble CD14, and those two figures are not compatible: 64 residues weigh about 7 kDa at the usual mean residue mass, so the 13 kDa is an apparent mass on gel electrophoresis for a glycosylated peptide. Neither can be chosen over the other honestly, and no laboratory reports presepsin in molar units.
What presepsin level indicates sepsis?
There is no agreed figure. Five published studies give cut-offs of 317, 415, 600, 600 and 729 pg/mL, a 2.3-fold spread. A result above the 55–184 pg/mL reference interval but below the lowest of those is common and genuinely ambiguous, and this page prints all five rather than presenting one as the answer.
Does kidney function affect presepsin?
Yes. Presepsin is cleared renally, so impaired kidney function raises it independently of infection. That matters because renal impairment is common in the patients in whom sepsis is suspected, and it is a confounder the number itself cannot show.
Related calculators
References
- Tosoh Bioscience. ST AIA-PACK Presepsin product information. (Presepsin defined as “the 13 KDa (64 amino acids) N terminal fragment of soluble form of CD14”; measuring range 2.98–20,000 pg/mL.)
- Giavarina D, Carta M. Determination of reference interval for presepsin, an early marker for sepsis. Biochem Med (Zagreb). 2015;25(1):64–8. doi:10.11613/BM.2015.007
- UniProt Knowledgebase entry P08571 (CD14, human): 375 residues, 40,076 Da precursor, signal peptide 1–19, N-glycosylation at Asn37 — inside the 64-residue fragment measured as presepsin.
Not medical advice. For healthcare professionals and education. Reference intervals vary by laboratory and assay — always use your own laboratory's. Never base a dose or a treatment decision on this page alone. Full disclaimer at calcengines.com/disclaimer/