CYFRA 21-1 Unit Converter
CYFRA 21-1 Unit Converter
ng/mL and µg/L are the same number for CYFRA 21-1. A soluble fragment of cytokeratin 19, used for prognosis and monitoring in non-small-cell lung cancer — never to diagnose it.
CYFRA 21-1 converter
Mass ladder onlyCYFRA 21-1 1.8 ng/mL
Formula and conversion factors
pg/mL = ng/mL × 1000
- ng/mL = µg/L
- a nanogram per millilitre and a microgram per litre are the same concentration, so no arithmetic is involved between them
- no molar unit
- CYFRA 21-1 measures a soluble fragment of cytokeratin 19 of no fixed size, quantified against an assay calibrator rather than weighed, so there is no molecular mass to divide by
- assay dependence
- cut-offs differ between manufacturers and are raised further in populations with benign lung disease, so serial results are only comparable on one platform
Worked example
CYFRA 21-1 1.8 ng/mL
1.8 ng/mL = 1.8 µg/L — the two units are identical
1.8 × 1000 = 1,800 pg/mL
No band is shown: the cut-off printed on your own report is the one that applies
The three units
| Unit | Relationship | Example |
|---|---|---|
| ng/mL | The usual reporting convention | 1.8 |
| µg/L | Identical to ng/mL | 1.8 |
| pg/mL | ng/mL × 1000 | 1,800 |
What CYFRA 21-1 is and is not for
| Use | Verdict |
|---|---|
| Screening for lung cancer | No. It is raised by benign lung disease and normal in many cancers |
| Diagnosing a lung nodule | No. A nodule is characterised by imaging and biopsy whatever the marker shows |
| Prognosis in non-small-cell lung cancer | Yes. A high level before treatment is an independent adverse prognostic factor in large pooled analyses |
| Monitoring known disease | Yes, alongside imaging — a falling level during treatment tends to track objective response |
| Distinguishing squamous from other histology | Partly. It performs best in squamous cell carcinoma, but it cannot assign histology on its own |
| Comparing results between laboratories | No. Cut-offs and calibration differ, so a trend is valid only on one assay |
A fragment of cytokeratin 19, and what it can honestly do
CYFRA 21-1 is reported in ng/mL and in the numerically identical µg/L, so nothing has to be calculated between them; pg/mL is simply a thousand times larger. There is no molar column. The assay detects a soluble fragment of cytokeratin 19, a structural filament protein released when epithelial cells break down, and the circulating fragment has no fixed length or mass. It is quantified against the assay’s own calibrator, which is also why the numbers are not transferable between manufacturers.
Its home is non-small-cell lung cancer, and particularly squamous cell carcinoma, where it is the single most useful of the conventional serum markers. That usefulness is specific and limited. A high pre-treatment level is an independent adverse prognostic factor, shown in a meta-analysis of more than two thousand patients, and a falling level during treatment tends to accompany objective response, so serial measurement adds something to imaging in disease that is already diagnosed.
What it cannot do is find cancer. Cytokeratin 19 fragments are released by any process that destroys epithelium, so chronic obstructive pulmonary disease, pneumonia, tuberculosis, bronchiectasis, interstitial lung disease and pleural inflammation all raise CYFRA 21-1 with no tumour present, and reduced renal clearance raises it again. In the other direction, plenty of lung cancers never raise it. A raised result therefore cannot rule a cancer in and a normal one cannot rule it out; a lung nodule is characterised by imaging and biopsy regardless of the marker.
This page shows no reference band because there is no honest universal one to show. Published cut-offs are manufacturer figures, and studies have repeatedly found that the optimal threshold shifts upward in populations with a high prevalence of benign lung disease. Use the interval on your own report, keep serial samples on one assay, and take the number to the clinician who has the scan. A tumour marker is one input into an assessment; it is never a diagnosis by itself.
Frequently asked questions
Is ng/mL the same as µg/L for CYFRA 21-1?
Yes, exactly the same number — a nanogram per millilitre is a microgram per litre. Only pg/mL differs, being a thousand times larger, so 1.8 ng/mL is 1.8 µg/L and 1,800 pg/mL. There is no molar unit for CYFRA 21-1.
What is CYFRA 21-1?
It is a soluble fragment of cytokeratin 19, a structural filament protein of epithelial cells, released into the blood when those cells break down. Because the circulating fragment has no fixed size it is measured against an assay calibrator rather than by mass, which is why no molar conversion exists.
Can CYFRA 21-1 diagnose lung cancer?
No. It is raised by chronic obstructive pulmonary disease, pneumonia, tuberculosis, bronchiectasis, interstitial lung disease and renal impairment, and it is normal in many lung cancers. Its established roles are prognosis and monitoring in disease that has already been diagnosed.
Why does this page not show a normal range?
Because the published cut-offs are manufacturer figures for individual analysers, and studies have shown the best threshold also depends on how much benign lung disease is present in the population being tested. The interval printed on your own report is the one that applies.
Does a high CYFRA 21-1 mean the cancer is worse?
A high level before treatment is an independent adverse prognostic factor in pooled analyses of non-small-cell lung cancer, but it describes an average across large groups, not an individual outcome. Prognosis is set by stage, histology, performance status and treatment response, which is a conversation for the treating team.
Related calculators
References
- Pujol JL, Molinier O, Ebert W, et al. CYFRA 21-1 is a prognostic determinant in non-small-cell lung cancer: results of a meta-analysis in 2,063 patients. Br J Cancer. 2004;90(11):2097–2105.
- Holdenrieder S, Wehnl B, Hettwer K, et al. Carcinoembryonic antigen and cytokeratin-19 fragments for assessment of therapy response in non-small cell lung cancer: a systematic review and meta-analysis. Br J Cancer. 2017;116(8):1037–1045.
- ARUP Consult. CYFRA 21-1 (cytokeratin 19 fragment) in lung cancer: test fact sheet. Salt Lake City: ARUP Laboratories.
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.