Procalcitonin Unit Converter
Procalcitonin Unit Converter
ng/mL and µg/L are the same number for procalcitonin, and every published threshold is written in them. The molar figure is arithmetically exact at 78.17 pmol/L per ng/mL and used by nobody.
Procalcitonin converter
ng/mL = µg/LProcalcitonin 0.35 ng/mL
Units and conversion factor
pg/mL = ng/mL × 1,000
pmol/L = ng/mL × 78.1677
- ng/mL and µg/L
- the same number. A nanogram per millilitre is a microgram per litre — the thousandfold step down in mass is cancelled by the thousandfold step up in volume. United States reports tend to use ng/mL, European ones µg/L, and every published threshold is quoted in one or the other
- 78.1677
- the molar factor, derived from procalcitonin’s molecular weight of 12,793 Da: 1 ng/mL is 10⁻⁶ g/L, and 10⁻⁶ ÷ 12,793 = 7.817 × 10⁻¹¹ mol/L, which is 78.17 pmol/L
- 12,793 Da
- procalcitonin is residues 26–141 of UniProt P01258, the 116-residue peptide left when the 25-residue signal sequence is cleaved from the 141-residue precursor. Summing those 116 residues from standard average residue masses gives 12,796, a 0.03% difference
- a caution the arithmetic hides
- the Association for Clinical Biochemistry states that there is no agreed reference method for procalcitonin and no reference material. Every platform is calibrated against the original luminometric immunoassay, which makes the unit conversion exact and the comparability between assays a separate matter
Worked example
Procalcitonin 0.35 ng/mL
0.35 ng/mL = 0.35 µg/L — identical numbers, no arithmetic
0.35 × 1,000 = 350 pg/mL
0.35 × 78.1677 = 27.36 pmol/L
Back the other way: 27.36 ÷ 78.1677 = 0.35 ng/mL, which is the round trip the unit grid above performs
The healthy-adult ceiling of 0.05 ng/mL is 50 pg/mL and 3.91 pmol/L
The 10 ng/mL figure at the top of the interpretation range is 782 pmol/L — the factor is the same at both ends, because a molar conversion is a straight multiplication
The same values in every unit on this page
| Significance | ng/mL (µg/L) | pg/mL | pmol/L |
|---|---|---|---|
| Healthy adults, high-sensitivity assay | under 0.05 | under 50 | under 3.9 |
| Systemic bacterial infection not likely | under 0.5 | under 500 | under 39 |
| Systemic bacterial infection possible | 0.5 to 2 | 500 to 2,000 | 39 to 156 |
| Systemic bacterial infection likely | 2 to 10 | 2,000 to 10,000 | 156 to 782 |
| Important systemic inflammatory response | 10 or more | 10,000 or more | 782 or more |
Where the two sources disagree, and why
| Source | Figure given for an adult | What it is actually describing |
|---|---|---|
| Thermo Fisher B·R·A·H·M·S PCT reference card | under 0.05 µg/L | normal values measured with a high-sensitivity assay |
| Association for Clinical Biochemistry monograph | 0.05 ng/mL or less | healthy individuals — the same number in the other unit |
| A reference laboratory’s own report comment | under 0.5 µg/L | the sepsis-unlikely decision threshold, quoted as if it were a reference interval |
What procalcitonin measures, and what the units hide
Procalcitonin is the 116-residue precursor of calcitonin. In health it is made almost exclusively by thyroid C cells and cleaved immediately, so almost none reaches the circulation and a healthy adult sits below 0.05 ng/mL. In a systemic bacterial infection that changes: cells throughout the liver, lung, kidney and gut transcribe the gene in response to bacterial endotoxin and to interleukin-6 and tumour necrosis factor, and release the uncleaved precursor, which can rise a thousandfold or more. Viral infection instead drives interferon-γ, which suppresses that induction — the whole reason procalcitonin interests antibiotic stewardship.
The kinetics matter more than any single value. Procalcitonin begins rising three to six hours after the stimulus and peaks at about twenty-four, so a normal early result does not exclude a response still coming. Its half-life is roughly a day, which makes serial measurement informative where one value is not: a falling value tracks a resolving infection faster than C-reactive protein, whose rise is slower and fall slower still.
The trap is specificity. Procalcitonin marks a systemic inflammatory response, not bacteria. It rises in the first two days of life, after major surgery, trauma, burns and cardiac arrest, in cardiogenic shock, in severe renal impairment where clearance falls, and in medullary thyroid carcinoma and small-cell lung cancer, which make it constitutively. It can also stay low in a genuine localised infection — an abscess, endocarditis, osteomyelitis — because the systemic signal is small. Neither error is corrected by a unit conversion.
The units themselves are kinder. ng/mL and µg/L are the same number, so the commonest question about procalcitonin units has no arithmetic in it. The molar conversion is exact — 78.17 pmol/L per ng/mL, from a molecular weight of 12,793 Da — and used by nobody, so it is here to decode a figure met elsewhere. The thresholds belong on a separate page: the procalcitonin interpreter for the stewardship bands, and the Sepsis-3 criteria for where a biomarker does and does not enter the definition of sepsis. Intervals and thresholds are method- and laboratory-dependent, and your own report’s interval, for the assay that produced the result, takes precedence.
Frequently asked questions
Is ng/mL the same as µg/L for procalcitonin?
Yes — numerically identical, so 0.35 ng/mL and 0.35 µg/L mean exactly the same thing. United States laboratories tend to report ng/mL and European ones µg/L, and every published threshold is quoted in one or the other without conversion.
How do I convert procalcitonin to pmol/L?
Multiply the ng/mL figure by 78.17. The factor comes from procalcitonin’s molecular weight of 12,793 Da — residues 26 to 141 of UniProt P01258, the 116-residue peptide. No laboratory actually reports procalcitonin in molar units, so the conversion is for decoding a figure seen elsewhere.
What is a normal procalcitonin level?
Below 0.05 ng/mL in an apparently healthy adult measured on a high-sensitivity assay. Thermo Fisher’s B·R·A·H·M·S reference card and the Association for Clinical Biochemistry monograph give that figure independently. Be careful of reports quoting “under 0.5” as a reference interval: that is the sepsis-unlikely decision threshold, which is a different kind of number and tenfold higher.
Are procalcitonin results from different analysers comparable?
Not fully. The Association for Clinical Biochemistry states that there is no agreed reference method for procalcitonin and no reference material; every platform is calibrated against the original luminometric immunoassay. The unit conversion is exact; a change of analyser is not a change in the patient.
Can procalcitonin be raised without bacterial infection?
Often — in the first two days of life, after major surgery, trauma, burns or cardiac arrest, in cardiogenic shock, in severe renal impairment, and in medullary thyroid carcinoma and small-cell lung cancer. It can also stay low in a localised infection such as an abscess or endocarditis.
Related calculators
References
- Thermo Fisher Scientific. B·R·A·H·M·S PCT Reference Card. (“Determination of normal values with a high sensitive assay revealed normal values to be below 0.05 µg/L”; interpretation bands at 0.5, 2 and 10 µg/L.)
- Association for Clinical Biochemistry. Procalcitonin (serum, plasma), analyte monograph. (Healthy individuals ≤ 0.05 ng/mL; “there is currently no agreed reference method for procalcitonin” and “no reference material is currently available”.)
- UniProt Knowledgebase entry P01258 (CALCA, human): preprocalcitonin, 141 residues, 15,467 Da, signal peptide 1–25 — so procalcitonin is residues 26–141, 116 residues.
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/