HLA-DR mismatch mattered after lung transplant, but only for two indications

Design

retrospective registry cohort study with multivariate Cox regression, stratified by indication

Population

37,091 lung transplant recipients in the UNOS/OPTN database

Primary outcome

graft survival by HLA mismatch category

Effect

HLA-DR mismatch graft failure HR 1.38 (95% CI 1.00–1.90) at 1 year; 2.88 (1.34–6.19) in COPD recipients

Lung allocation does not use HLA matching, because organs are scarce and transplants are urgent. Whether matching would help at all — and for whom — is therefore a risk-stratification question rather than an allocation one. This retrospective cohort analysed 37,091 lung transplant recipients in the UNOS/OPTN database, grouped by HLA mismatch (0 to 2 against 3 to 6) and stratified by transplant indication.

HLA-DR mismatch was associated with higher graft failure at one year (hazard ratio 1.38, 95% CI 1.00 to 1.90, p=0.048) and at five years (1.20, 1.03 to 1.40, p=0.020). Stratification showed the effect confined to two indications. In recipients transplanted for COPD, one-year graft failure risk rose sharply with mismatch (2.88, 1.34 to 6.19, p=0.007); in interstitial pneumonia, five-year risk rose (1.28, 1.03 to 1.58, p=0.026). No comparable signal appeared in other indications.

Because matching is not used in allocation, the actionable part is downstream. If HLA-DR mismatch predicts graft failure specifically in COPD and interstitial pneumonia recipients, then donor-specific antibody surveillance and immunosuppression intensity in those groups are where the finding lands. That is a hypothesis for a protocol change, not a protocol change — the analysis is registry-based and the one-year overall estimate has a lower bound sitting exactly on 1.00.

• Record the HLA-DR mismatch count in the recipient's notes even though it did not affect allocation
• Consider more intensive donor-specific antibody surveillance in mismatched COPD and interstitial pneumonia recipients
• Do not extrapolate to other indications — the effect was absent there
• Note the overall one-year estimate is borderline, with a lower confidence bound of exactly 1.00
• Treat this as a rationale for a prospective study, not for changing immunosuppression today

Why it matters

It offers a way to risk-stratify after transplant using information that allocation already discards.

Don't overread it

This is registry data — HLA-DR mismatch predicts graft failure here, which is not the same as showing that matching would prevent it.

The statistics, in plain English

The overall one-year hazard ratio of 1.38 has a lower bound of exactly 1.00 and p=0.048, which is the weakest kind of positive. The COPD subgroup figure of 2.88 looks dramatic but its interval runs from 1.34 to 6.19, reflecting a small number of events — subgroup estimates in registry analyses are where spurious findings concentrate. What makes this more credible than a typical subgroup claim is that the same direction appeared at both time points and in two biologically related indications.

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