Chronic obstructive pulmonary disease: diagnosis and staging

01OverviewDefinition, clinical context and the essential points that orientate the chapter.

COPD is persistent, usually progressive airflow obstruction associated with an abnormal inflammatory response to inhaled exposures. Diagnosis requires both the clinical syndrome and objective post-bronchodilator obstruction; radiographic emphysema and chronic bronchitis can exist with different degrees of spirometric impairment.

Staging serves different purposes. FEV1 describes airflow impairment, the MRC scale describes activity-related breathlessness, and exacerbation history describes future attack risk. Management decisions draw on all three plus eosinophilic/asthmatic features, comorbidity and patient goals.

Diagnostic review is essential when the pattern is atypical: marked day-to-day variability, onset under 35, no exposure, haemoptysis, clubbing, weight loss, rapid decline or symptoms disproportionate to spirometry.

Key points

Think COPD in adults over 35 with smoking or occupational exposure plus exertional breathlessness, chronic cough, regular sputum, frequent winter bronchitis or wheeze.
Confirm with quality-assured post-bronchodilator spirometry showing FEV1/FVC below 0.70 in the appropriate clinical context.
A fixed ratio can overdiagnose older adults and miss some younger adults; use the lower limit of normal and diagnostic review when symptoms and ratio disagree.
NICE airflow grades use post-bronchodilator FEV1: mild at least 80% predicted, moderate 50-79%, severe 30-49%, very severe below 30%.
FEV1 grade does not equal symptom burden or prognosis. Record MRC dyspnoea, exacerbations, admissions, oxygenation, BMI, exercise capacity and comorbidity separately.
Obstruction can be asthma, bronchiectasis, post-TB disease or bronchiolitis; a large variability history, atopy/eosinophilia or childhood symptoms may indicate asthma or coexistence.
CXR excludes alternative structural disease but does not confirm COPD; CT is targeted to diagnostic uncertainty, disproportionate symptoms, bronchiectasis or procedural/surgical assessment.
Test alpha-1 antitrypsin in younger people, minimal smokers, those with a family history or basal-predominant emphysema; confirm abnormal levels with genotype/phenotype specialist pathways.
Ask about occupational dusts/fumes and biomass, not only cigarettes; quantify pack-years and offer evidence-based tobacco-dependence treatment at every opportunity.
Document the diagnosis as a synthesis: exposure + symptoms + persistent obstruction + impact/phenotype, not 'FEV1 45%' alone.

02AetiologyUnderlying causes, associations and risk factors, with why each one matters.

Tobacco smoke

Long-term active smoking is the dominant UK exposure, with risk shaped by intensity, duration, early-life lung development and individual susceptibility.

Occupational and environmental exposure

Dusts, fumes, biomass smoke and air pollution contribute cumulative airway and alveolar injury, particularly when combined with tobacco exposure.

Alpha-1 antitrypsin deficiency

Inherited severe deficiency permits unopposed protease activity and early emphysema, especially with smoking, and should be considered in a compatible phenotype or family history.

Impaired lung development

Prematurity, childhood respiratory disease and disadvantage may limit peak attained lung function, allowing persistent obstruction to emerge without unusually rapid adult decline.

03PathophysiologyThe causal sequence from the underlying abnormality to symptoms and harm.

1
Chronic airway inflammation
Repeated inhaled injury recruits inflammatory cells, thickens small-airway walls and increases mucus production, progressively narrowing conducting airways.
2
Loss of elastic recoil
Alveolar wall destruction reduces the radial traction that holds small airways open, causing expiratory collapse and gas trapping.
3
Hyperinflation
Incomplete emptying raises resting lung volume and flattens the diaphragm, increasing the work of breathing and limiting inspiratory reserve during exercise.
4
Gas-exchange impairment
Uneven obstruction and emphysematous capillary loss create ventilation-perfusion mismatch, leading to hypoxaemia and, in advanced ventilatory failure, carbon dioxide retention.

04Clinical features and red flagsSymptoms, examination findings, patterns of presentation and time-critical warnings.

Typical COPD syndrome

Age over 35, cumulative tobacco/occupational exposure, progressive exertional dyspnoea, chronic cough/sputum, wheeze and winter exacerbations, with persistent post-bronchodilator obstruction.

Chronic bronchitis phenotype

Productive cough for at least 3 months in each of 2 consecutive years after excluding other causes. It can coexist with emphysema and signals exacerbation/mucus burden but is not synonymous with obstruction.

Emphysema-predominant disease

Hyperinflation, reduced breath sounds, low BMI or reduced gas transfer, with low-attenuation change on CT when imaged. Consider alpha-1 antitrypsin deficiency if young, minimally exposed or basal predominant.

Asthmatic/steroid-responsive features

Previous secure asthma/atopy, substantial FEV1 variation (for example at least 400 mL), or higher eosinophils may alter inhaler choice. Do not use a single small reversibility result to invent an overlap label.

05InvestigationsWhat to request, why it matters and how to interpret it.

Investigation order

Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.

01
Post-bronchodilator spirometryFirst step
Why
Confirm persistent airflow obstruction.
Interpretation and limitations
FEV1/FVC below 0.70 supports COPD in a compatible adult. Grade post-BD FEV1 as mild ≥80%, moderate 50-79%, severe 30-49%, very severe <30%, while noting LLN and test quality.
02
CXR
Why
Exclude alternative structural disease and identify hyperinflation or complications.
Interpretation and limitations
May show hyperinflation, flattened diaphragms or bullae but can be normal. A mass, fibrosis, cardiomegaly, effusion or focal opacity redirects investigation.
03
Full blood count, BMI and oxygen saturation
Why
Identify anaemia/polycythaemia, cachexia/obesity and hypoxaemia.
Interpretation and limitations
SpO2 at or below 92% when stable, cyanosis, polycythaemia, oedema or severe obstruction prompts formal arterial-blood-gas assessment for LTOT eligibility.
04
MRC dyspnoea and exacerbation history
Why
Measure functional burden and future risk.
Interpretation and limitations
MRC 3 or more supports pulmonary-rehabilitation offer. Count steroid/antibiotic-treated and hospital exacerbations over 12 months; distinguish true attacks from heart failure or anxiety.
05
Blood eosinophils and asthma history
Why
Identify features suggesting corticosteroid responsiveness and eligibility for newer specialist therapy.
Interpretation and limitations
Use repeated/historical values with treatment and exacerbation context. Eosinophils ≥0.3 x10^9/L plus uncontrolled disease on dual/triple therapy meets the biomarker element of NICE TA1142 dupilumab criteria.
06
Alpha-1 antitrypsin
Why
Find inherited deficiency where presentation is early, exposure is limited or family/imaging pattern suggests it.
Interpretation and limitations
A low serum level requires specialist confirmation with phenotype/genotype, family counselling and avoidance of smoking; inflammation can raise measured levels.
07
CT chest, ECG/BNP/echo or sputum microbiology when targeted
Why
Resolve disproportionate symptoms, focal findings or recurrent infection.
Interpretation and limitations
CT defines emphysema/bronchiectasis and cancer pathways; cardiac tests assess competing dyspnoea. Routine sputum culture is not needed when stable unless purulence/recurrent infection suggests it.

06Differential diagnosisRealistic alternatives and the features that help distinguish them.

Asthma

Marked symptom variability, atopy and objective variability or reversibility favour asthma, whereas COPD obstruction is persistent; neither a single bronchodilator result nor age alone decides.

Bronchiectasis

Large-volume purulent sputum, recurrent infection and bronchial dilatation on CT point towards bronchiectasis, which may coexist with COPD.

Heart failure

Orthopnoea, oedema, cardiac signs and congestion on imaging support heart failure, while spirometry should be interpreted after acute fluid overload settles.

Interstitial lung disease

Fine crackles, clubbing, restrictive physiology and interstitial change on imaging argue for parenchymal fibrosis rather than primary obstructive airway disease.

Lung cancer

Haemoptysis, weight loss, focal chest signs or a new radiographic lesion require investigation for malignancy rather than attribution to chronic COPD symptoms.

Additional chapter-specific clues

Alternative or additional diseaseRed flag

Clubbing, focal signs, haemoptysis, very large sputum volume, systemic features, rapid decline or disproportionate hypoxaemia suggests cancer, bronchiectasis, ILD, TB, heart failure or pulmonary vascular disease.

07ManagementImmediate care, first-line treatment, alternatives and escalation.

01ConfirmFrom suspicion to documented COPDFirst stepCompatible symptoms and exposure history.

1Take exposure, symptom, exacerbation, childhood/asthma, occupational and family history; examine for wheeze, hyperinflation, cyanosis, oedema, cachexia, clubbing and cardiac disease.
2Perform quality-assured post-bronchodilator spirometry when stable. Confirm persistent obstruction only when FEV1/FVC below 0.70 fits the syndrome; review LLN in borderline or age-discordant cases.
3Obtain CXR, FBC, BMI and resting SpO2; add ECG/BNP, CT, full physiology or microbiology when the presentation is atypical or disproportionate.
4Document FEV1 grade, MRC score, exacerbation/admission count, smoking status, oxygenation and asthmatic/eosinophilic features as separate management domains.

02MismatchSymptoms and spirometry disagreeSevere symptoms with mild obstruction, marked obstruction with few symptoms, or a borderline ratio.

1Recheck test quality, reference range and clinical stability; repeat post-bronchodilator spirometry if technically limited or performed during illness.
2Investigate heart failure/ischaemia, anaemia, obesity/deconditioning, ILD, pulmonary vascular disease, bronchiectasis, cancer and dysfunctional breathing based on clues.
3Use lung volumes/gas transfer, CT, exercise assessment or cardiac testing selectively; do not intensify COPD inhalers indefinitely when the mechanism is elsewhere.

03Young/minimal exposureLook beyond ordinary smoking-related COPDOnset under about 40-45, little tobacco exposure, family clustering or basal emphysema.

1Revisit asthma, bronchiectasis, obliterative bronchiolitis, cystic fibrosis, post-TB disease, occupational exposure and connective-tissue/ILD causes.
2Measure alpha-1 antitrypsin and refer abnormal or strongly suspected cases for genotype/phenotype confirmation and family advice.
3Use CT/full physiology and respiratory specialist review; aggressively prevent further inhaled exposure and optimise vaccination/rehabilitation while the cause is clarified.

04At diagnosisActions that should not wait for inhaler selectionCOPD confirmed or strongly supported.

1Offer tobacco-dependence treatment, explain diagnosis and inhaler purpose, and provide self-management/exacerbation advice.
2Review vaccination eligibility, nutrition/activity, occupational exposure and comorbid cardiovascular disease, anxiety/depression and osteoporosis.
3Offer pulmonary rehabilitation when functionally limited (usually MRC ≥3) and arrange annual review of symptoms, exacerbations, technique, smoking and oxygenation.

Key medicines and prescribing safety2 treatments · regimens, roles and cautions

Treats tobacco dependence; combination long-acting plus short-acting NRT is more effective than a single form for many people.

Nicotine replacement combination

Example: nicotine patch delivering 21 mg/24 h daily for heavier dependence plus a rapid product such as 2 mg gum or lozenge when cravings occur; taper over roughly 8-12 weeks according to response and product directions.

Individualise to cigarettes/day, time to first cigarette, pregnancy and cardiovascular context; avoid smoking while using more nicotine than intended and teach correct gum/lozenge technique. Link to behavioural support.

Short-acting bronchodilator for intermittent symptom relief.

Salbutamol symptom reliever while full plan is established

100-200 micrograms inhaled when required, commonly 1-2 actuations of a 100 microgram pMDI; frequency and maximum follow the specific SmPC.

Rising use signals poor control or another diagnosis. Tremor, tachycardia and hypokalaemia can occur; ensure technique and do not use response as diagnostic proof.

08ComplicationsImportant consequences, why they occur and why they matter clinically.

Acute exacerbations

Infective or environmental insults can abruptly worsen airway inflammation, symptoms and gas exchange, accelerating functional decline and prompting hospital admission.

Respiratory failure

Advanced ventilation-perfusion mismatch and pump overload cause chronic hypoxaemia, sometimes with hypercapnia, pulmonary vascular stress and vulnerability to acute decompensation.

Pulmonary hypertension

Chronic hypoxic vasoconstriction, vascular remodelling and loss of capillary bed can raise pulmonary pressure and eventually strain the right ventricle.

Frailty and cachexia

Breathlessness, systemic inflammation and inactivity drive skeletal-muscle loss, reduced exercise capacity and poorer resilience to further illness.

Pneumothorax

Rupture of emphysematous bullae can produce secondary spontaneous pneumothorax, causing disproportionate physiological compromise in limited respiratory reserve.

09Monitoring and follow-upTreatment response, safety checks and longer-term review.

Review at least annually: MRC dyspnoea, exacerbation/admission count, smoking/exposure, BMI, SpO2, inhaler technique, adherence and comorbidity.
Repeat spirometry when diagnosis is uncertain, symptoms change unexpectedly or a result will change management; routine frequent repetition is not a substitute for clinical review.
Monitor weight loss, oedema, polycythaemia, oxygen saturation and signs of pulmonary hypertension or cor pulmonale.
Track eosinophil history and steroid exposure when considering ICS, triple therapy or specialist biologic treatment.
Ensure a clear exacerbation plan and check that repeated 'exacerbations' are not recurrent heart failure, pulmonary emboli or bronchiectasis infection.

10Special situationsVariants, exceptions and circumstances that change the usual approach.

FEV1 and breathlessness answer different questions

Airflow impairment predicts some outcomes but activity limitation is also shaped by hyperinflation, muscle deconditioning, cardiac disease, anxiety and anaemia.

The fixed ratio needs judgement

FEV1/FVC naturally falls with age. A value just below 0.70 in an asymptomatic older non-smoker deserves review, not automatic lifelong COPD labeling.

Clubbing is not routine COPD

Look for lung cancer, bronchiectasis, ILD or another cause rather than attributing it to emphysema.

Reversibility does not divide asthma from COPD cleanly

Some COPD varies and some treated asthma is fixed. Use longitudinal symptoms, exposure, atopy/eosinophils and magnitude/history—not one bronchodilator test.

Diagnosis creates prevention opportunities

Smoking treatment, pulmonary rehabilitation, vaccination and cardiovascular risk care often produce more benefit than arguing over a narrow FEV1 category.

11Common pitfallsFrequent interpretation and management errors.

01
Diagnosing COPD from symptoms, CXR hyperinflation or pre-bronchodilator spirometry alone.
02
Using FEV1 stage as the whole severity assessment.
03
Ignoring LLN and clinical context around a borderline ratio.
04
Attributing clubbing, haemoptysis or weight loss to uncomplicated COPD.
05
Missing alpha-1 antitrypsin deficiency in a young or minimally exposed patient.
06
Assuming every acute breathlessness episode is a COPD exacerbation.