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Open questions — chronic obstructive pulmonary disease¶
Last curated: 2026-10-27 (periodic sweep; OQ-33 and OQ-43 sharpened, none closed)
Stable identifiers are retained when questions are refined. Tier 1 questions could change practice and are designable now; Tier 2 questions need enabling methods, longer follow-up or mechanistic validation.
Tier 1 — practice-changing and designable now¶
OQ-1 — Which symptomatic/exposed case-finding strategy improves outcomes, not only diagnostic yield?¶
Questionnaires and micro-spirometry enrich confirmatory testing, but studies primarily measure new diagnoses rather than exacerbations, quality of life or net treatment change (Haroon 2015, PMID 26313400; Frith 2020, PMID 31950588).
OQ-2 — What repeat-spirometry rule should adjudicate values near FEV1/FVC 0.70?¶
Fixed-ratio simplicity trades against age-related misclassification; a prospective repeat-testing rule could measure stable labels, treatment changes and outcomes (Haynes 2023, PMID 37353330).
OQ-3 — Which PRISm/pre-COPD subgroup has a modifiable trajectory?¶
Early-state constructs are heterogeneous and lack validated intervention thresholds (Li 2025, PMID 40624819; Cadham 2024, PMID 38750492).
OQ-4 — Can repeated eosinophils guide ICS initiation and withdrawal better than a single count?¶
Eosinophil–outcome associations are continuous, while SUNSET suggests withdrawal risk rises in higher-count subgroups (Yun 2018, PMID 29709670; Chapman 2018, PMID 29779416). For biologics, a pooled METREX/METREO/MATINEE analysis found mepolizumab benefit with variable as well as persistently elevated counts, and no benefit with persistently low counts (<150/µL) (Criner 2026, PMID 42265988). It is a post hoc analysis of sponsor trials, and whether the same rule holds for ICS decisions is untested.
OQ-5 — How should ICS and dupilumab be sequenced in type-2 COPD?¶
Dupilumab benefit was demonstrated on background triple therapy, so efficacy as an ICS-sparing strategy is unknown (Bhatt 2023, PMID 37272521; Bhatt 2024, PMID 38767614).
OQ-6 — Can eosinophil-guided systemic steroids safely reduce acute steroid exposure in hospitalized exacerbations?¶
CORTICO-COP supports reduced steroid exposure in hospitalized exacerbations, while STARR2 extends biomarker-directed treatment to primary care; severe-event precision and subgroup safety remain unresolved (Sivapalan 2019, PMID 31122894; Ramakrishnan 2024, PMID 37924830).
OQ-7 — Which discharge bundle prevents 30- and 90-day readmission?¶
Medication reconciliation, early follow-up and rehabilitation are bundled variably; component effects remain unclear (MacLeod 2021, PMID 33893708; Puhan 2016, PMID 27930803).
OQ-8 — What post-exacerbation PR start window maximizes benefit and acceptability?¶
Post-event PR evidence is heterogeneous and real-world uptake is low (Puhan 2016, PMID 27930803).
OQ-9 — Can minimal-equipment or hybrid PR match center-based outcomes without widening digital inequity?¶
Minimal-equipment programs improve outcomes, but comparative durability and access effects need pragmatic trials (Cheng 2023, PMID 37140475).
OQ-10 — Which moderate/exertional desaturation phenotype benefits from ambulatory oxygen?¶
LOTT was neutral for death/first hospitalization; individual functional response may not predict durable patient-important benefit (Albert 2016, PMID 27783918). In a 2026 single-session crossover trial, pulsed 1–2 L/min portable-concentrator oxygen was not better than ambient air for 6-minute walk distance (difference 0 m, 95% CI −14 to 13), though dyspnoea was lower and 5 of 40 patients gained >35 m (Lichtblau 2026, PMID 42767802). The phenotype question now includes the delivery device: pulsed portable delivery may not reproduce continuous-flow benefit.
OQ-11 — What PaCO2 threshold and timing best select long-term home NIV after an exacerbation?¶
HOT-HMV supports persistent post-event hypercapnia, but selection and titration differ across services (Murphy 2017, PMID 28528348; Ergan 2019, PMID 31467119).
OQ-12 — Which eligible emphysema patients should receive valves rather than LVRS?¶
CELEB directly randomized 88 people eligible for either procedure and found no significant difference in 12-month i-BODE improvement; only 49 had complete primary outcomes, leaving patient-level selection and precision unresolved (Buttery 2023, PMID 36796833).
OQ-13 — Which CT rule predicts durable five-year valve benefit and pneumothorax risk?¶
Fissure integrity predicts initial response, while long-term durability and early pneumothorax remain variable (Criner 2018, PMID 29787288; Koster 2022, PMID 35562097).
OQ-14 — Does universal COPD testing for AATD improve case detection and family outcomes cost-effectively?¶
Guidelines recommend broad testing, yet detection remains incomplete (Miravitlles 2017, PMID 29191952; Brantly 2020, PMID 32306990).
OQ-15 — Which severe AATD population obtains survival or exacerbation benefit from augmentation?¶
CT-density evidence and observational survival associations do not fully resolve hard outcomes (Strange 2018, PMID 29794204; Fraughen 2023, PMID 37624745). The 2026 Cochrane update (6 RCTs, 526 randomized) found no mortality difference (OR 0.30, 95% CI 0.03–2.98; low certainty) and a possible slight increase in exacerbations with IV augmentation (MD +0.29/year, 0.04–0.54; low certainty) (Glaister 2026, PMID 42626936). The question is sharper: the registry survival signal has no randomized counterpart, and the only pooled randomized exacerbation estimate points the other way. A trial with a hard-outcome primary endpoint, or a registry analysis emulating a target trial, is now the decisive design.
OQ-16 — Can integrated cardiopulmonary assessment reduce misclassified COPD exacerbations?¶
Cardiac and respiratory causes overlap, and COPD deaths frequently involve cardiovascular disease (Halpin 2024, PMID 39078244).
OQ-17 — Which oxygen-service design preserves mobility and reduces treatment burden?¶
Equipment burden is recognized but rarely a primary randomized endpoint (Taichman 2024, PMID 39254439).
OQ-18 — Which stigma intervention improves help-seeking or rehabilitation uptake?¶
COPD-specific stigma measurement is early; a PubMed search on 2026-08-30 retrieved no intervention trial linking stigma reduction to help-seeking or rehabilitation uptake (Woo 2023, PMID 37084465).
Tier 2 — enabling science and longer horizons¶
OQ-19 — Which small-airway measurement best predicts incident obstruction?¶
Small-airway loss can precede conventional COPD, but thresholds and longitudinal treatment relevance are unsettled (Verleden 2024, PMID 38055196).
OQ-20 — Are machine-derived CT emphysema subtypes reproducible and treatment-predictive?¶
Unsupervised clusters describe anatomy but need external and prospective validation (Angelini 2023, PMID 37268414).
OQ-21 — Which tissue immune communities sustain emphysema after smoking cessation?¶
Spatial transcriptomics identifies B-cell-rich structures without proving causation (Rojas-Quintero 2024, PMID 37934672).
OQ-22 — Why did IL-4Rα blockade outperform IL-5 strategies in eosinophilic COPD?¶
Mepolizumab effects were modest/inconsistent while dupilumab phase 3 results replicated (Pavord 2017, PMID 28893134; Bhatt 2024, PMID 38767614).
OQ-23 — Can neutrophilic inflammation be treated without increasing infection?¶
Neutrophils contribute proteases and mucus biology but are indispensable host defense (Brightling 2019, PMID 31073084).
OQ-24 — Can human alveolar repair be activated safely?¶
FGF10 reversed experimental emphysema in mice; translation must address fibrosis, cancer and delivery (Hadzic 2023, PMID 37884305).
OQ-25 — How much COPD arises from low attained lung function rather than accelerated adult decline?¶
Life-course development and aging provide multiple routes to the same late spirometry (Bush 2016, PMID 28005431).
OQ-26 — Can ancestry-diverse polygenic prediction add value beyond exposure, spirometry and CT?¶
COPD GWAS discovery is substantial but clinical calibration and ancestry representation are inadequate (Silverman 2020, PMID 31730394).
OQ-27 — What exposure reduction from clean household energy changes lung-function trajectory?¶
Biomass associations are heterogeneous, and intervention adoption/exposure separation is difficult (Kurmi 2010, PMID 20335290; Pathak 2020, PMID 30754998).
OQ-28 — Can MRI provide a standardized multicenter functional surrogate?¶
Regional ventilation/perfusion imaging is mechanistically attractive but not validated for treatment decisions (Elbehairy 2024, PMID 38548292).
OQ-29 — Which regenerative-cell product has a defined mechanism and acceptable long-term safety?¶
Early registries include bronchial basal-cell and small-mobile-cell approaches, but completed status is not efficacy (NCT03021681; NCT06986070).
OQ-30 — What COPD outcome core set should all trials report?¶
Patient-reported outcomes are selected inconsistently, frustrating meta-analysis and patient interpretation (Afroz 2020, PMID 32801678).
OQ-31 — Can intervention be matched to the two major lung-function trajectories before fixed obstruction appears?¶
Approximately half of COPD arose from low attained early-adult FEV1 and half from accelerated decline after normal attainment; the latter route had higher all-cause mortality (HR 1.93, 95% CI 1.14–3.26) in long-term follow-up (Lange 2015, PMID 26154786; Marott 2020, PMID 32289231). A designable platform could stratify by repeated early-adult spirometry and randomize exposure, asthma or development-focused interventions before both routes converge on late obstruction.
OQ-32 — Is CT mucus-plug burden a modifiable causal trait or only a severity marker?¶
Mortality rose from 34.0% with no plugged segments to 54.1% with at least three over median 9.5 years, but observational adjustment cannot show that clearing plugs changes outcomes (Diaz 2023, PMID 37210745). A 2026 meta-analysis of 7 cohorts (15,702 patients) confirmed a graded exacerbation association, with a severe-exacerbation HR of 1.41 (1.04–1.91) for high-grade plugs; the high-grade mortality HR of 1.48 (0.86–2.54) was imprecise (Pu 2026, PMID 42097456). The JRS 2026 guideline now treats plugging as an independent prognostic factor (Sugiura 2026, PMID 42447589). Prognostic acceptance has therefore moved ahead of any interventional evidence, and the dupilumab plug trial (NCT07053423, recruiting) remains the first direct test. Trials should require plug reduction plus exacerbation, activity and mortality-linked outcomes, not imaging response alone.
OQ-33 — Which head-to-head biologic sequence maximizes net benefit in type-2 COPD?¶
Dupilumab produced replicated benefit, MATINEE showed a smaller mepolizumab exacerbation effect without significant symptom/QoL improvement, benralizumab primary phase 3 comparisons were neutral, and COURSE did not establish broad tezepelumab efficacy (Bhatt 2024, PMID 38767614; Sciurba 2025, PMID 40305712; Criner 2019, PMID 31112385; Singh 2025, PMID 39653044). Indirect cross-trial comparison cannot establish sequence, switching or ICS-sparing effects. Update 2026-10-27: comparative observational evidence now exists: a US matched cohort found no statistically significant exacerbation difference between dupilumab and mepolizumab or benralizumab. Missing eosinophils/spirometry, asthma–COPD overlap and confounding by indication prevent a treatment ranking; randomized comparisons and switching/sequence studies remain needed (Liao 2026, PMID 42928777; full-text Tables 1–2, Methods and Conclusions).
OQ-34 — Where should ensifentrine sit relative to LABA/LAMA, triple therapy and rehabilitation?¶
ENHANCE replicated 87–94 mL FEV1 AUC benefit and moderate/severe-event rate ratios of 0.64 and 0.57, but symptom and SGRQ effects did not replicate across both trials (Anzueto 2023, PMID 37364283). Pragmatic factorial comparison on contemporary background treatment should measure exacerbations, symptoms, device burden, cost and discontinuation.
OQ-35 — Can an integrated frailty–bone–rehabilitation pathway improve outcomes beyond separate screening?¶
Frailty prevalence pooled at 32.07% and carried mortality HR 1.68, while osteoporosis prevalence pooled at 38%; both estimates varied by population and definition (Wang 2023, PMID 37173728; Chen 2019, PMID 31352034). A trial could randomize systematic identification plus nutrition, resistance training, falls and bone treatment against usual fragmented care.
OQ-36 — Does targeted cardiovascular surveillance after exacerbation prevent events?¶
Cardiovascular-event hazard was 3.8-fold higher in the first 30 days after an exacerbation and 9.9-fold higher after a hospitalized event in SUMMIT participants with cardiovascular disease or risk (Kunisaki 2018, PMID 29442524). The association identifies a designable window but not the effective surveillance or preventive intervention.
OQ-37 — Can oscillometry improve diagnostic access without substituting one threshold problem for another?¶
Small cross-sectional studies report AUCs near 0.8 against spirometry or CT, but cutoffs vary with BMI and positive predictive value can be low (Chaiwong 2020, PMID 33121279; Chen 2024, PMID 38187302; Klitgaard 2023, PMID 36836082). A pragmatic diagnostic trial should compare completed diagnostic pathways, false labels, cost and downstream outcomes—not only same-day discrimination.
OQ-38 — Can airway NET inhibition reduce virus-triggered exacerbation without impairing host defense?¶
Human rhinovirus challenge links NET burden to exacerbation severity and mouse NETosis/DNase experiments support causal immunopathology, but NETs also contain infection (Katsoulis 2024, PMID 38982052; Keir 2022, PMID 35197267). Early trials need pathogen clearance and secondary infection as co-primary safety domains.
OQ-39 — Which treatment-burden intervention increases capacity rather than merely transferring work home?¶
Qualitative syntheses identify fragmented pathways, navigation work, isolation and caregiver capacity as determinants of COPD treatment burden (Lippiett 2019, PMID 30813114; May 2016, PMID 27707824). Co-designed trials should measure patient and caregiver time, abandonment of care, social participation and equity alongside utilization.
OQ-40 — Which post-exacerbation cardiovascular intervention matches the timing and phenotype of risk?¶
A 213,466-person cohort found the cardiovascular hazard highest in days 1–14 after severe events (HR 14.5, 95% CI 12.2–17.3) but peaking in days 14–30 after moderate events, with different component outcomes (Graul 2024, PMID 38127850). This sharpens OQ-36 from surveillance in general to severity- and time-specific prevention.
OQ-41 — Which component of an early-diagnosis pathway changes outcomes in COPD specifically?¶
Case-finding plus pulmonologist and educator care reduced respiratory health-care use by 52%, but the randomized population combined newly diagnosed asthma and COPD and bundled diagnosis with treatment (Aaron 2024, PMID 38767248). A COPD-specific factorial design should separate prescreening, confirmatory testing, clinician expertise and self-management support.
OQ-42 — Is a Proteobacteria-dominant airway microbiome a cause, consequence or treatment marker?¶
Longitudinal sampling links viral events and bacterial dominance to exacerbation, while stable Proteobacteria dominance predicts mortality (Bouquet 2020, PMID 32228581; Dicker 2021, PMID 32353489). Perturbation studies must distinguish pathogen clearance from ecological harm and stratify antibiotics, ICS exposure and bronchiectasis.
OQ-43 — Does smoking status identify an IL-33-pathway-responsive COPD endotype?¶
Itepekimab missed its overall exacerbation endpoint but showed a prespecified former-smoker signal, whereas astegolimab also missed its overall endpoint (Rabe 2021, PMID 34302758; Yousuf 2022, PMID 35339234). Replication must test a treatment-by-smoking-status interaction rather than treating the subgroup estimate as efficacy. Partly answered (2026-10-20): in phase 3, tozorakimab's overall-population rate ratios (0.70 OBERON, 0.71 TITANIA) were almost identical to its former-smoker primary-endpoint ratios (0.71, 0.66) (Sciurba 2026, PMID 42708515). Astegolimab's phase 2b and phase 3 trials gave the same point estimate (RR 0.85), and only the phase 2b result was significant (Papi 2026, PMID 42150581). At the level of headline estimates, smoking status does not look like a strong effect modifier for tozorakimab. A formal interaction estimate and the eosinophil-low subgroup remain open. Registry-results synthesis 2026-10-27: itepekimab Q2W reduced the primary exacerbation rate in AERIFY-1 (RR 0.729, 95% CI 0.598–0.890), but not in the AERIFY-2 former-smoker primary cohort (0.984, 0.803–1.206). These posted primary-outcome tables show that former-smoker enrichment alone did not produce replicated benefit; they do not test the treatment-by-smoking-status interaction (NCT04701983; NCT04751487; v2 API retrieved 2026-10-27). A peer-reviewed phase 3 results report was not identified in the targeted PubMed query this date.
OQ-44 — Can ambulatory-oxygen benefit be predicted jointly with real-world acceptability?¶
Short-term quality of life improved in a small crossover trial, yet acute exercise response did not predict longer response and 41% of acute or short-term responders declined continued oxygen (Eaton 2002, PMID 12212960). Trials should co-model physiological response, device weight, mobility, stigma and abandonment.
OQ-45 — Which inhaler errors are causally important and correctable?¶
Nineteen COPD studies provided only weak, confounded evidence linking aggregate error counts to clinical outcomes, with adherence usually unmeasured (Halpin 2024, PMID 38626929). Sensor-supported trials should randomize correction of prespecified critical errors and measure exacerbations and quality of life, not technique scores alone.
Dots not yet connected¶
| # | Dot A | Dot B | The missing junction | Powers |
|---|---|---|---|---|
| 2 | In COPDGene, CT plugs in ≥3 versus 0 segments carried crude mortality of 54.1% versus 34.0% over median 9.5 years, adjusted HR 1.24 (95% CI 1.10–1.41) (PMID 37210745) | In COPD with blood eosinophils ≥300/μL, dupilumab reduced annualized moderate/severe exacerbations to 0.86 versus 1.30 with placebo (rate ratio 0.66, 95% CI 0.54–0.82; PMID 38767614) | No COPD biologic trial has yet published plug outcomes (PubMed, 2026-10-07; a 2026 review states the same, PMID 42072432). Whether treatment reduces plugs is now being tested in registered randomized trials of dupilumab (NCT07053423, recruiting, primary endpoint week-24 CT mucus score) and mepolizumab (NCT07749001, not yet recruiting). Neither is designed to test whether baseline plug burden modifies exacerbation benefit. | OQ-5, OQ-22 |
| 3 | Eosinophil-guided acute steroids in hospitalized exacerbations shortened median exposure from 5 to 2 days; 30-day treatment failure was 26% in both arms (PMID 31122894) | In non-frequent exacerbators withdrawn from ICS, SUNSET found an overall exacerbation rate ratio of 1.08 (95% CI 0.83–1.40), with higher risk in the ≥300 eosinophils/μL subgroup (PMID 29779416) | No study in the searched PubMed records has tested whether eosinophil behavior during an acute admission predicts the later benefit or harm of chronic ICS withdrawal. The acute and maintenance decisions were studied separately. | OQ-4, OQ-5, OQ-6 |
| 4 | In MESA (2,816 adults without very severe disease), each 10-point increase in CT percent emphysema was associated with left ventricular end-diastolic volume −4.1 mL (95% CI −3.3 to −4.9) and cardiac output −0.19 L/min (PMID 20089972) | In 24 patients after endobronchial valves, right ventricular end-diastolic volume index rose 7.9 mL/m² and cardiac output 0.9 L/min at 8 weeks (PMID 35584341). An 85-study review judged lung volume reduction's overall cardiac effect inconclusive (PMID 40174955). | Deflation improves cardiac filling physiology, but no valve or LVRS study in PubMed or Europe PMC (searched 2026-10-07) reports cardiovascular events or heart-failure hospitalization as an outcome. The registered cardiac study NCT04556942 measures endothelial function only. | OQ-12, OQ-16 |
| 6 | In the Swedish neonatal-screening AATD cohort at age 37–40, 4% of PiZZ subjects versus 12% of population controls were current smokers (P = 0.008; PMID 28203073) | When adult smokers were tested for AATD at home, a severe-deficiency result raised 24-hour quit attempts (59% versus 26% with a normal result) but did not change 3-month abstinence (PMID 17291167) | Testing of first-degree relatives is now recommended (PMID 39880301). However, no study in PubMed or Europe PMC (searched 2026-10-07) measures sustained abstinence, non-initiation or COPD avoided in relatives identified by cascade testing. The evidence covers neonatal identification and short-term behavior in tested adults only. | OQ-14, OQ-15 |
| 7 | A Cochrane review of 15 telerehabilitation studies (1,904 participants, 99% with COPD) reported programme completion of 93% (95% CI 90–96%) for telerehabilitation against 70% for in-person rehabilitation (PMID 33511633) | A COPD stigma scale derived 24 items from 148 participants (α = 0.93) and discriminated supplemental-oxygen users (p < 0.001) (PMID 37084465). A 29-study qualitative synthesis links stigma to reduced help-seeking and non-compliance (PMID 40126301). | No searched PubMed record has used a measured stigma construct as the target or mediator of an intervention to raise rehabilitation start or completion. | OQ-9, OQ-18 |
| 8 | Spatial profiling of 115 lymphoid follicles from 40 ever-smokers and COPD patients found an emphysema-associated abnormal B-cell activation signature (q = 2.56 × 10⁻¹¹¹; PMID 37934672) | Unsupervised CT analysis identified six reproducible emphysema subtypes (interlearner ICC 0.91–1.00) with differing prognosis (PMID 37268414) | The tissue studies are cross-sectional, including a 141-participant single-nucleus and spatial atlas (PMID 41578022). No searched longitudinal study maps tissue immune niches to subsequent regional CT subtype progression. | OQ-20, OQ-21 |
| 18 | In SUMMIT participants with COPD and cardiovascular disease or risk, the cardiovascular-event HR was 3.8 (95% CI 2.7–5.5) in the 30 days after an exacerbation and 9.9 (6.6–14.9) in the 30 days after a hospitalized exacerbation (PMID 29442524) | Eight post-exacerbation rehabilitation trials (810 patients) pooled to a readmission OR of 0.44 (95% CI 0.21–0.91, I² = 77%; PMID 27930803) | No randomized trial in PubMed or ClinicalTrials.gov (searched 2026-10-07) has tested a discharge rehabilitation or monitoring pathway with adjudicated 30-day cardiovascular events as an outcome. Registered studies with MACE endpoints are non-randomized: NCT06723795 (in-exacerbation cardiovascular assessment, MACE at 3 and 6 months) and NCT06379529 (virtual-first service, MACE at 12 months). | OQ-7, OQ-16, OQ-36 |
| 27 | Of 19 COPD inhaler-error studies (6,487 patients), 15 were low quality and most were confounded by unmeasured adherence (PMID 38626929) | In Japanese claims data, the proportion adherent (PDC ≥80%) at 6 months was 19.7% with single-inhaler versus 10.2% with multiple-inhaler triple therapy (PMID 39632104) | One completed trial combined electronic adherence-and-technique monitoring with patient outcomes: biofeedback raised actual adherence by 18 percentage points over inhaler demonstration (95% CI 6–30) at month 2 and lowered SGRQ by 6.1. It enrolled a mixed asthma/COPD population (55 of 152 with COPD) and did not target prespecified critical errors (PMID 31568927). No completed COPD-specific trial randomizes correction of critical errors with objective dose-taking and exacerbation outcomes. | OQ-8, OQ-17, OQ-45 |