DLCO Correction for Haemoglobin Calculator

An uncorrected DLCO reads low in anaemia for a reason that is not the lung. The published haemoglobin adjustment, the reference haemoglobin it is anchored on, and both directions the two standards use.

Last updated 8 Oct 2026

DLCO corrected for haemoglobin

2017 ERS/ATS equations 31 to 33

Measured DLCO (mL/min/mmHg)The measured single-breath DLCO as the report prints it. The units cancel in the percentage this page returns, so a consistent pair of measured and predicted values in mmol/min/kPa works just as well as mL/min/mmHg.

Predicted DLCO, from the reportThe unadjusted predicted DLCO for this patient, in the same unit as the measured value. This page cannot generate a predicted value. The GLI equations are spline models that need age-specific coefficients interpolated from a published table, and the calculator engine here has no table interpolation — so the predicted value is taken from your report rather than approximated, which is the only version that can be right. Predicted values, LLNs and z-scores are reference-set dependent — GLI 2012, GLI Global, NHANES III and ECSC disagree for the same person — so use the set your own report names.

HaemoglobinHaemoglobin at the time of the test, with the unit set below. Entering a g/L figure with the unit left at g/dL is the mistake this page refuses rather than absorbs; the haemoglobin unit converter covers the three units in circulation.

Haemoglobin unitThe published equation takes g/dL, so the other two units are converted first. The mmol/L factor is the standard’s own: it gives the male reference haemoglobin as 14.6 g/dL (9 mmol/L) and the female as 13.4 g/dL (8.26 mmol/L), and both pairs yield 1.6222 g/dL per mmol/L.

Reference haemoglobin for this patientThis is where the correction most often goes wrong. The equation is anchored on a reference haemoglobin and the 2017 ERS/ATS standard gives two: 14.6 g/dL for adolescent and adult males, 13.4 g/dL for adult females and children under 15. The published constants 10.22 and 9.38 are simply 0.7 times those two values.

71.4percent of haemoglobin-adjusted predictedExample

Measured DLCO 18.0, predicted 30.0, haemoglobin 10.0 g/dL, male 15 and over

Formula

DLCO predicted for Hb = DLCO predicted × 1.7 Hb ÷ (0.7 Hb_ref + Hb)
with Hb in g/dL, Hb_ref = 14.6 for males 15 and over and 13.4 for females and children under 15

the published form: the 2017 ERS/ATS single-breath CO standard prints three equations: 1.7 Hb ÷ (10.22 + Hb) for adolescent and adult males, 1.7 Hb ÷ (9.38 + Hb) for females and children under 15, and the general 1.7 Hb ÷ (0.7 Hb_ref + Hb). Since 10.22 is 0.7 × 14.6 and 9.38 is 0.7 × 13.4, the three are one equation
Hb_ref, and where this goes wrong: 14.6 g/dL (9 mmol/L) for adolescent and adult males, 13.4 g/dL (8.26 mmol/L) for adult females and children under 15. The factor is exactly 1 at Hb = Hb_ref, which is the check that the right anchor is in use; applying the male anchor to a woman at Hb 10 g/dL makes the adjustment 4.3% too large
which value is adjusted: the 2017 standard: “it is recommended that adjustments for these factors be made in the predicted rather than the measured DLCO value”. The 2005 standard adjusted the MEASURED value instead, as DLCO ÷ (1.7 Hb ÷ (10.22 + Hb)) — the exact inverse, printed above. Instruments ship with either convention
a third variant that is not the inverse: a widely circulated rearrangement puts the reference haemoglobin in the numerator — DLCO × 1.7 Hb_ref ÷ (Hb + 0.7 Hb_ref) — which agrees with the published inverse at Hb = Hb_ref and nowhere else. At a haemoglobin of 10 g/dL in a man it gives 1.2275 against the correct 1.1894, 3.2% apart. Check which form an implementation uses before trusting it
carboxyhaemoglobin, a separate adjustment: equation 37 of the same standard gives predicted DLCO × (102% − COHb%), about 1% per percentage point of COHb above 2%, recommended only where COHb is known or suspected above 2%

Worked example

Measured DLCO 18.0, predicted 30.0, haemoglobin 10.0 g/dL, male 15 and over
Reference haemoglobin for this row is 14.6 g/dL, so the denominator constant is 0.7 × 14.6 = 10.22 — the figure printed in the standard's equation 31
Factor = 1.7 × 10.0 ÷ (10.22 + 10.0) = 17 ÷ 20.22 = 0.8408
Adjusted predicted DLCO = 30.0 × 0.8408 = 25.22
Percent predicted, unadjusted = 18.0 ÷ 30.0 = 60.0%
Percent predicted, adjusted = 18.0 ÷ 25.22 = 71.4%. The anaemia accounted for 11.4 percentage points of an apparently reduced gas transfer
Three points, not one. At 14.6 g/dL the factor is 24.82 ÷ 24.82 = exactly 1.0000, the check that the right anchor is in use; at 7.0 g/dL it is 11.9 ÷ 17.22 = 0.6911; at 18.0 g/dL it is 30.6 ÷ 28.22 = 1.0843, so the correction runs both ways
The anchor matters. On the female and child row, reference haemoglobin 13.4 g/dL, the factor becomes 17 ÷ 19.38 = 0.8772, the adjusted predicted 26.32 and the percent predicted 68.4% instead of 71.4%. Using the wrong row shifts the answer by about three percentage points
The 2005 direction. Correcting the measured value instead gives 18.0 × 1.1894 = 21.41 against the unadjusted predicted 30.0, the same 71.4% — algebraically identical, and differing only in which column of the report moves
Enter a haemoglobin of 100 with the unit left at g/dL and the page refuses rather than returning a figure: no haemoglobin is 100 g/dL, and the equation is not defined there

The adjustment factor on both anchors

Every factor is this page’s own arithmetic from the published equation. Each column reads exactly 1.0000 at its own anchor, the test of whether the right row was selected, and the last column is the cost of choosing wrongly — largest where the anaemia is worst, which is where it matters most.
Haemoglobin (g/dL)	Factor, male anchor 14.6	Factor, female and child anchor 13.4	Gap between the two
7.0	0.6911	0.7265	5.1%
10.0	0.8408	0.8772	4.3%
13.4	0.9644	1.0000	3.7%
14.6	1.0000	1.0350	3.5%
18.0	1.0843	1.1176	3.1%

Three adjustments on one DLCO

This page computes the first. The other two are named because a report showing an unexplained gap from a previous one has usually changed an adjustment rather than a lung.
Adjustment	Published form	Applied when
Haemoglobin	predicted × 1.7 Hb ÷ (0.7 Hb_ref + Hb), Hb in g/dL	Always — the 2017 standard requires all interpretations to have the reference values adjusted for haemoglobin content
Carboxyhaemoglobin	predicted × (102% − COHb%)	Where COHb is known or suspected to be above 2%, which it is in any current smoker tested within hours of a cigarette
Inspired oxygen or altitude	a separate correction on the inspired oxygen tension	Where the test is performed away from sea level or on supplemental oxygen; a laboratory at altitude applies it routinely

Why an anaemic DLCO reads low, and which reference haemoglobin anchors it

The single-breath DLCO measures how fast carbon monoxide disappears from alveolar gas, and it disappears by binding to haemoglobin. The measurement therefore depends on how much haemoglobin is in the pulmonary capillary bed as well as on the membrane and the capillary volume. An anaemic patient has a genuinely reduced transfer factor and it is genuinely not a lung problem, which is why the 2017 ERS/ATS standard states that all interpretations must have the reference values adjusted for haemoglobin content.

The adjustment has a published form and two anchors. The standard gives 1.7 Hb ÷ (10.22 + Hb) for adolescent and adult males, 1.7 Hb ÷ (9.38 + Hb) for females and children under 15, and a general 1.7 Hb ÷ (0.7 Hb_ref + Hb) where a better reference haemoglobin is available — which shows the two constants are 0.7 times the reference haemoglobins of 14.6 and 13.4 g/dL. The factor is exactly 1 at the anchor, the quickest check that the right row was chosen; choosing wrongly is the commonest error here, and at a haemoglobin of 10 g/dL the two anchors differ by 4.3%.

The two standards disagree about which number to move. The 2017 standard adjusts the predicted value explicitly; the 2005 standard adjusted the measured value by the exact algebraic inverse. The percent predicted is the same either way, so this is a reporting convention rather than a disagreement about physiology — but a report’s corrected-DLCO column may hold either, instruments ship with both, and comparing across a change of convention produces a change in the patient that did not happen. A third rearrangement circulates with the reference haemoglobin in the numerator; it is not the inverse of the published equation and is 3.2% out at a haemoglobin of 10 g/dL.

Predicted values, lower limits of normal and z-scores are reference-set dependent: GLI 2012, the race-neutral GLI Global average equations, NHANES III and the older ECSC equations give different predicted values for the same person, and a result can cross a threshold purely because the laboratory changed reference set. Read this against the set printed on your own report. This page prints no severity bands for DLCO: the 2022 ERS/ATS standard grades gas transfer on the z-score rather than on percent predicted, and that needs the report’s own lower limit of normal, which the percent predicted and z-score converter will take. This supports a clinician’s judgement rather than replacing it.

Frequently asked questions

What is the haemoglobin correction for DLCO?

The 2017 ERS/ATS single-breath CO standard multiplies the predicted DLCO by 1.7 Hb ÷ (0.7 Hb_ref + Hb), with haemoglobin in g/dL and a reference haemoglobin of 14.6 g/dL for males aged 15 and over or 13.4 g/dL for females of any age and children under 15. Those two anchors are what produce the familiar constants 10.22 and 9.38.

Which reference haemoglobin should I use?

14.6 g/dL for adolescent and adult males, 13.4 g/dL for adult females and children under 15, as the standard specifies. Using the male anchor for a woman at a haemoglobin of 10 g/dL makes the adjustment 4.3% larger than it should be. The check is simple: the factor must come out as exactly 1 when the haemoglobin equals the anchor.

Should the measured or the predicted DLCO be corrected?

The 2017 standard adjusts the predicted value and recommends that explicitly. The 2005 standard adjusted the measured value by the exact inverse, and instruments still ship with either convention. The percent predicted is identical either way, so the practical issue is knowing which column of your report has moved.

Do laboratories report the corrected or the uncorrected DLCO?

It varies. The 2017 standard requires a system to be able to report the unadjusted measured DLCO and to report any adjustments with the data used to make them, but a report may print either value or both — and one that gives only one, with no haemoglobin beside it, cannot be checked.

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References

Graham BL, Brusasco V, Burgos F, et al. 2017 ERS/ATS standards for single-breath carbon monoxide uptake in the lung. Eur Respir J. 2017;49(1):1600016.
Stanojevic S, Kaminsky DA, Miller MR, et al. ERS/ATS technical standard on interpretive strategies for routine lung function tests. Eur Respir J. 2022;60(1):2101499.
ndd Medical Technologies. Adjustment of DLCO Measurements (EasyOne Connect application note). Zurich: ndd, 2021.
MSD Manual Professional Edition. Diffusing capacity for carbon monoxide (DLCO) corrected for anemia — medical calculator. Rahway, NJ: Merck & Co.
Nowosad R. pft: Diffusion capacity (DLCO / TLCO): reference, Hb correction, interpretation — package vignette. Comprehensive R Archive Network, 2024.

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/