Pentraxin-3 (PTX3) Unit Converter
Pentraxin-3 (PTX3) Unit Converter
ng/mL and µg/L are the same number for PTX3, and healthy values are low enough that pg/mL is common. No molar conversion is offered: the sources disagree on how many subunits PTX3 even has.
Pentraxin-3 (PTX3) converter
ng/mL = µg/LPTX3 0.44 ng/mL
Units, and why there is no molar column
pg/mL = ng/mL × 1,000
- ng/mL and µg/L
- the same number. Both appear in the PTX3 literature, usually without comment, because no conversion is needed between them
- pg/mL
- the ng/mL figure × 1,000, and the unit most healthy-range PTX3 figures are quoted in: a healthy median of 0.44 ng/mL reads more naturally as 438 pg/mL. Mixing the two is the commonest error here
- no nmol/L
- the sources do not agree on a mass, or on the structure the mass belongs to. UniProt P26022 gives a 41,976 Da precursor and a disulfide-linked HOMOOCTAMER; Inforzato and colleagues give a 45 kDa glycosylated protomer, 40 kDa deglycosylated, assembled as a DECAMER of about 900 kDa by size-exclusion chromatography; a later review gives an octamer of two tetramers at roughly 320 to 360 kDa
- a revision worth knowing
- PTX3 was originally assumed to share C-reactive protein’s architecture, a non-covalent pentamer of 23 kDa subunits. It does not: the interface residues that make CRP pentameric are absent and the subunits are joined covalently. A structure revised more than once is itself a reason not to bake a mass into a calculator
Worked example
PTX3 0.44 ng/mL
0.44 ng/mL = 0.44 µg/L — identical numbers, no arithmetic
0.44 × 1,000 = 440 pg/mL, which is how the healthy median of 438 pg/mL is usually quoted
Back again: 440 ÷ 1,000 = 0.44 ng/mL, the round trip the grid above performs
The indicative healthy ceiling of 2 ng/mL is 2,000 pg/mL
The septic shock median of 22 ng/mL is 22,000 pg/mL, and the non-survivor figure of 205 ng/mL is 204,879 pg/mL as the source prints it
Health and septic shock are about fifty-fold apart, and health and the worst outcomes about five hundred-fold — which is why a PTX3 figure always needs its unit attached
PTX3 concentrations, in both units
| Population | ng/mL (µg/L) | pg/mL | Source |
|---|---|---|---|
| Apparently healthy adults, indicative | under 2 | under 2,000 | Albert Vega et al 2019 (“barely detectable” in health) |
| Healthy volunteers, median | 0.44 | 438 | same source, measured |
| Septic shock, day 3 to 4, median | 22 | 22,031 | same source, measured |
| Septic shock non-survivors, reported figure | 205 | 204,879 | same source, measured |
Five masses for one molecule, and the sources behind each
| Mass | What it describes | Source |
|---|---|---|
| 40 kDa | deglycosylated protomer | Inforzato 2006; Balhara 2013 |
| 41,976 Da | the precursor, 381 residues including a 17-residue signal peptide | UniProt P26022 |
| 45 kDa | glycosylated protomer, glycan about 10% of the mass | Inforzato 2006 |
| About 320 to 360 kDa | disulfide-linked octamer, two tetramers | UniProt P26022 subunit annotation; Balhara 2013 |
| About 900 kDa | native mass by size-exclusion chromatography, described as a decamer | Inforzato 2006 |
The pentraxin that is already made before the liver hears about it
Pentraxin-3 belongs to the same family as C-reactive protein, and the comparison is the fastest way to understand it. CRP is a short pentraxin, synthesised by hepatocytes in response to interleukin-6, which is why it takes the better part of a day to rise. PTX3 is a long pentraxin and is not synthesised on demand at all: it is stored pre-formed in the specific granules of neutrophils and released within minutes of those cells meeting microbial products or inflammatory cytokines, with endothelium, macrophages, dendritic cells and fibroblasts making more over the following hours.
That changes what the number means. PTX3 peaks several hours before CRP does, and because it comes from the tissue rather than the liver it reports local inflammation at the site of injury rather than a hepatic summary of it. Functionally it is a soluble pattern recognition molecule: it binds C1q, ficolin-2 and factor H and so tunes complement activation, binds selected fungi and bacteria — Aspergillus fumigatus most notably — and is involved in matrix remodelling and female fertility.
Clinically it is strongly prognostic in sepsis and almost entirely non-specific. In health it is barely detectable, median around 440 pg/mL; in septic shock at day three to four one study found a median of 22 ng/mL, fifty times higher, and values above 200 ng/mL in those who did not survive. It also rises in acute coronary syndromes, heart failure, vasculitis, pre-eclampsia and after surgery, and no published concentration makes a diagnosis or indicates a treatment. PTX3 assays are research assays with no common calibrator, so a value is interpretable against that assay’s own distribution and the patient’s earlier results, and not much else.
The units carry one trap and one refusal. The trap is that healthy values are below 1 ng/mL, so most normal-range figures are quoted in pg/mL while septic ones are quoted in ng/mL — a thousandfold difference inside one literature. The refusal is the molar column: the published masses run from 40 kDa to 900 kDa and the sources do not agree whether the native protein is an octamer or a decamer, so there is no grams-per-mole to divide by. The table above prints all five figures with their sources instead. 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 ng/mL the same as µg/L for PTX3?
Yes — numerically identical. The conversion that matters is to pg/mL, which is a thousand times the ng/mL figure: a healthy PTX3 of 0.44 ng/mL is 440 pg/mL, and because healthy values sit below 1 ng/mL most normal ranges are quoted in pg/mL while septic values are quoted in ng/mL.
Why is there no nmol/L conversion for pentraxin-3?
Because the sources disagree on the mass and on the structure it belongs to. UniProt gives a 41,976 Da precursor as a disulfide-linked octamer; the structural work gives a 45 kDa glycosylated protomer, 40 kDa deglycosylated, in a decamer of about 900 kDa by size-exclusion chromatography; a later review gives an octamer of about 320 to 360 kDa. Those span twenty-two-fold, so no molar conversion is offered.
What is a normal PTX3 level?
PTX3 is barely detectable in health, generally under 2 ng/mL, with one study measuring a median of 438 pg/mL in healthy volunteers. PTX3 assays are research assays with no common calibrator, so treat that as indicative and use the distribution your own method reports.
How does PTX3 differ from CRP?
CRP is made by the liver in response to interleukin-6, so it takes most of a day to rise. PTX3 is stored ready-made in neutrophil granules and released within minutes, then produced by endothelium and macrophages at the site of inflammation. It peaks several hours earlier and reports local rather than hepatic inflammation.
Is there a PTX3 threshold for sepsis?
No published decision threshold exists, and the assays are not standardised against each other, so a single cut-off would not transfer. PTX3 is prognostic rather than diagnostic — it rises in acute coronary syndromes, heart failure, vasculitis, pre-eclampsia and after surgery as well as in sepsis.
Related calculators
References
- Albert Vega C, Mommert M, Boccard M, et al. Source of circulating pentraxin 3 in septic shock patients. Front Immunol. 2019;9:3048. doi:10.3389/fimmu.2018.03048
- Inforzato A, Peri G, Doni A, et al. Structure and function of the long pentraxin PTX3 glycosidic moiety: fine-tuning of the interaction with C1q and complement activation. Biochemistry. 2006;45(38):11540–51.
- Balhara J, Koussih L, Zhang J, Gounni AS. Pentraxin 3: an immuno-regulator in the lungs. Front Immunol. 2013;4:127. doi:10.3389/fimmu.2013.00127
- UniProt Knowledgebase entry P26022 (PTX3, human): 381 residues, 41,976 Da precursor, signal peptide 1–17, “Homooctamer; disulfide-linked”, N-glycosylation at Asn220.
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/