Lipopolysaccharide Binding Protein Unit Converter
Lipopolysaccharide Binding Protein Unit Converter
Convert LBP between µg/mL, mg/L and ng/mL — the first two are the same number. The honest framing belongs in the first paragraph rather than the last: LBP has been proposed as a sepsis marker for twenty-five years, and in a head-to-head emergency department study it performed like CRP and worse than procalcitonin.
LBP converter
Mass units onlyLBP 9 µg/mL
The ladder, and the units the literature mixes
1 µg/mL = 1,000 ng/mL
no nmol/L or pmol/L is offered
- µg/mL = mg/L
- a microgram in a millilitre is a milligram in a litre. The prefix and the volume both move by a thousand and cancel, so the number is unchanged. Papers on LBP use the two interchangeably within the same table, which is survivable precisely because they are identical
- ng/mL
- the µg/mL figure multiplied by 1,000. Used by some research ELISAs. A healthy LBP of about 8 µg/mL becomes 8,000 ng/mL, so a result in the thousands is not a high value — it is a different unit
- no molar unit
- LBP is a glycosylated acute-phase protein of roughly 60 kDa measured against an assay calibrator. Its molar mass is not the constant a conversion needs, so there is no nmol/L on this page
- µg/dL, if you meet it
- not offered here, and worth suspicion when you see it. At least one published LBP paper prints its cut-off in µg/dL in one table and its group medians in g/dL, which cannot both be right for an analyte whose healthy median is about 8 mg/L. Check the figure against the healthy range before using it
Worked example
LBP 9 µg/mL
9 µg/mL is 9.00 mg/L — the same number
9 × 1,000 = 9,000 ng/mL
Inside the 1.85–17.4 µg/mL healthy range from the series quoted above, close to its median of 7.94
Severe sepsis and septic shock in that same series had a median of 46.2 µg/mL at onset, roughly five times this figure
This number is not a triage tool. For the marker with published stewardship thresholds, use the procalcitonin interpreter
LBP against procalcitonin and CRP, head to head
| Marker | Area under the curve for diagnosing sepsis | Comparison |
|---|---|---|
| Procalcitonin | 0.844 (95% CI 0.769–0.90) | Better than LBP (P = 0.012) and better than CRP (P = 0.014) |
| CRP | 0.707 (95% CI 0.605–0.808) | Indistinguishable from LBP (P = 0.89) — see the CRP converter |
| LBP | 0.701 (95% CI 0.599–0.803) | Indistinguishable from CRP; worse than procalcitonin |
What the concentrations actually look like
| Population | Serum LBP | Notes from the same series |
|---|---|---|
| Healthy adults | 1.85 to 17.4 mg/L, median 7.94 mg/L | A ninefold span between the bounds, on one assay in one study |
| Severe sepsis or septic shock, at onset | Median 46.2 mg/L | Roughly a 10.5-fold rise over the healthy controls |
| Severe sepsis or septic shock, at peak | Median 83.1 mg/L | Peak reached at a median of 40 hours, range 1 to 120 hours |
What LBP is actually doing, which is more interesting than its performance
| Concentration | Effect on the LPS response |
|---|---|
| Low, physiological | LBP is the transfer protein that presents bacterial lipopolysaccharide to CD14, amplifying the monocyte response to endotoxin — this is the function the protein is named for |
| High, as in septic shock | The direction reverses. Excess LBP transfers LPS to lipoproteins, neutralising it, and drives CD14-dependent and CD14-independent cellular uptake without inflammatory activation |
| Demonstrated how | Depleting LBP from high-concentration septic serum restored LPS-induced TNF-α secretion, identifying LBP as the serum component responsible for the suppression |
A good story about endotoxin, and a test that has not earned a place
The conversion is trivial and worth two sentences. A microgram per millilitre and a milligram per litre are the same concentration — prefix and volume both change a thousandfold and cancel — so the number does not move between them, which is why the literature uses both within a single paper without comment. Nanograms per millilitre multiplies by a thousand, so a healthy LBP of around 8 µg/mL is 8,000 ng/mL; a four-figure LBP is a unit change and not a catastrophe. There is no molar unit, because LBP is a glycosylated 60 kDa acute-phase protein measured against a calibrator rather than a molar mass.
Lipopolysaccharide binding protein has an unusually good mechanistic story behind it. It is a hepatically synthesised acute-phase protein whose day job is to extract lipopolysaccharide from Gram-negative bacterial membranes and present it to CD14, which is the first step in the pathway that turns endotoxin into a systemic inflammatory response. A protein that sits at the head of that pathway and rises tenfold in sepsis looks, on paper, like the marker everyone wants. It has been studied as one for twenty-five years.
The measurements have been less obliging than the mechanism. In a prospective emergency department study of adults with suspected infection, the area under the curve for diagnosing sepsis was 0.701 for LBP, 0.707 for C-reactive protein and 0.844 for procalcitonin; procalcitonin beat both, and LBP and CRP could not be told apart. The authors’ conclusion is worth quoting rather than paraphrasing: in adult emergency department patients with suspected infection, the diagnostic accuracy for sepsis of LBP is similar to that of CRP but lower than that of procalcitonin. That is the state of the evidence, and it does not support LBP displacing either marker already in routine use. Two structural features of the analyte help explain why. The healthy range in the best-characterised series spans 1.85 to 17.4 mg/L — a ninefold spread, so an individual can rise substantially from their own baseline without leaving it. And the rise is slow: in severe sepsis the median concentration was 46.2 mg/L at onset and peaked at 83.1 mg/L a median of forty hours later, with individual peaks from one hour to five days. A marker that takes most of two days to declare itself is not the instrument for the first hour of a septic presentation, which is when the decision is made.
There is a further twist that makes LBP more interesting than its receiver operating curve. At the concentrations septic shock generates, LBP stops amplifying the endotoxin signal and starts suppressing it — transferring lipopolysaccharide to lipoproteins where it is neutralised, and driving cellular uptake without inflammatory activation. Depleting LBP from high-concentration septic serum restores the tumour necrosis factor response, which is about as direct a demonstration as immunology offers. So the same molecule whose concentration you are measuring is, at that concentration, part of how the response is being switched off. A quantity that is both a consequence of endotoxaemia and a brake on it is not going to map neatly onto severity, and it does not.
The practical position, then. If an LBP has been measured, convert it, read it as evidence of an acute-phase response rather than of infection specifically, and do not treat it as a triage number: no agreed decision threshold exists and it is not a routinely offered test in most laboratories. For the marker with published stewardship thresholds use the procalcitonin interpreter; for the cheap, universal and entirely non-specific acute-phase comparator use the CRP converter; for the marker that rises fastest of the three see the interleukin-6 converter; and for the definition of sepsis itself, which is organ dysfunction rather than any biomarker, the Sepsis-3 criteria interpreter.
Frequently asked questions
Is µg/mL the same as mg/L for LBP?
Yes, identical. A microgram in a millilitre is a milligram in a litre: the prefix and the volume both change by a factor of a thousand and cancel. Published papers on LBP move between the two labels freely for that reason. Nanograms per millilitre is the same figure multiplied by 1,000, so a healthy value of about 8 µg/mL is 8,000 ng/mL.
What is a normal LBP level?
There is no harmonised reference interval. The best-characterised series reports healthy adults at 1.85 to 17.4 mg/L with a median of 7.94 mg/L — a ninefold span between the bounds, which is itself part of the problem with using LBP as a decision variable. In the same study severe sepsis and septic shock had a median of 46.2 mg/L at onset. Use the interval printed beside your own result if there is one.
Is LBP better than procalcitonin or CRP for sepsis?
No. In a prospective emergency department study of adults with suspected infection the areas under the curve for diagnosing sepsis were 0.701 for LBP, 0.707 for CRP and 0.844 for procalcitonin. Procalcitonin was significantly better than both (P = 0.012 against LBP, P = 0.014 against CRP) while LBP and CRP were indistinguishable (P = 0.89). The authors concluded that LBP’s accuracy is similar to CRP’s and lower than procalcitonin’s.
How quickly does LBP rise in sepsis?
Slowly, which is a real limitation. In severe sepsis and septic shock the median concentration was 46.2 mg/L at onset and peaked at 83.1 mg/L after a median of 40 hours, with individual peaks anywhere between 1 and 120 hours. A marker whose peak is most of two days away is poorly matched to a decision that has to be made in the first hour, however impressive the eventual tenfold rise looks.
What does LBP actually do?
It extracts lipopolysaccharide from Gram-negative bacterial membranes and presents it to CD14, which is the first step in turning endotoxin into a systemic inflammatory response. At the high concentrations reached in septic shock the effect reverses: LBP transfers lipopolysaccharide to lipoproteins where it is neutralised and drives cellular uptake without inflammatory activation. Depleting LBP from septic serum restores the tumour necrosis factor response to endotoxin.
Is there a molar unit for LBP?
No, and there should not be. LBP is a glycosylated acute-phase protein of roughly 60 kDa measured against an assay calibrator rather than against a molar mass, so there is no single grams-per-mole to divide a mass concentration by. A nmol/L figure would be an assumed molecular weight presented as a unit conversion. Be wary too of results quoted in µg/dL: at least one published paper prints units that cannot all be correct for this analyte.
Related calculators
References
- García de Guadiana Romualdo L, Albaladejo Otón MD, Rebollo Acebes S, et al. Diagnostic accuracy of lipopolysaccharide-binding protein for sepsis in patients with suspected infection in the emergency department. Ann Clin Biochem. 2018;55(1). AUC: LBP 0.701 (0.599–0.803), CRP 0.707 (0.605–0.808), PCT 0.844 (0.769–0.90); PCT vs LBP P = 0.012, PCT vs CRP P = 0.014, LBP vs CRP P = 0.89. "In adult ED patients with suspected infection, the diagnostic accuracy for sepsis of LBP is similar to that of CRP but lower than that of PCT."
- Zweigner J, Gramm H-J, Singer OC, Wegscheider K, Schumann RR. High concentrations of lipopolysaccharide-binding protein in serum of patients with severe sepsis or septic shock inhibit the lipopolysaccharide response in human monocytes. Blood. 2001;98(13):3800–8. Healthy serum LBP 1.85–17.4 mg/L (median 7.94); severe sepsis median 46.2 mg/L at onset, peak 83.1 mg/L at a median of 40 hours (range 1–120 h); LBP depletion restored LPS-induced TNF-α secretion.
- Diagnostic accuracy of lipopolysaccharide-binding protein as biomarker for sepsis in adult patients: a systematic review and meta-analysis. PLoS One. 2016;11(4):e0153188.
- data/_factors.json, analyte
lbp: "Lipopolysaccharide binding protein, a ~60 kDa glycosylated acute-phase protein reported as a mass concentration; ug/mL and mg/L are identical." mwExempt — no mass-to-molar bridge.
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.