Table 2

Further investigations, suggestive signs and expected abnormal findings according to the underlying aetiology

AetiologySuggestive signsAdditional investigationsExpected abnormalities
Cystic fibrosisAge under 40, malabsorption, poor growth, infertility in males, faecal masses on abdominal x-ray, diabetesSweat testPositive sweat test: chloride concentration >60 mEq/l
Genetic testing2 CFTR mutations
NPDAbnormal NPD
Congenital disordersPrimary ciliary dyskinesia: sinusitis, otitis media, hearing loss, poor sense of smell, middle lobe predominanceNasal epithelial brushing or biopsyAbnormal ciliary beat pattern and frequency of ciliogenesis in culture
Nasal NO measurement (>5 years of age)Nasal NO <150 ppb
Saccharin test (no clinical value anymore)Increased time (>60 min) before tasting saccharin
Marfan's syndrome: myopia, arachnodactylia, tall stature, thoracic deformations, glaucoma, abnormal joint flexibility, heart murmurSearch for major and minor indicators of the disorderDiagnosis based on family history and a combination of major and minor indicators of the disorder, rare in the general population but occurring in one individual Genetic testing
α1-Antitrypsin deficiencyα1-Antitrypsin deficiencyLevels below 150 mg/dl
Anatomical deformations: visible on clinical examinationThoracic imagingScoliosis or pectus excavatum
IBDDiarrhoea, abdominal pain, haematochezia, weight loss, arthritis, pyoderma gangrenosum, primary sclerosing cholangitisColonoscopy with biopsy of pathological lesionsBiopsy inflammation suggestive of IBD
Gastrointestinal advice
Coeliac diseaseMalabsorption, chronic diarrhoea, failure to thrive in children, fatigue, mouth ulcers, anaemia, weight loss, dermatitis herpetiformistTG antibodies and IgAPositive tTG antibodies test without IgA deficiency
Endoscopic duodenal or jenunal biopsiesLymphocytic infiltration, villous atrophy
Post infectiousHistory of multiple pulmonary infections, tuberculosis or cough suppressionHistory or radiological evidence of previous infectionRadiological evidence of previous infection, history of cough suppression
Sputum with smear and culture for acid-fast bacilliPositive for Mycobacterium avium complex or other mycobacteria
Immunological disordersPrimary: recurrent infections, developmental delay in children, particular organ problemsIgG and subclasses, IgA, IgMDecreased values, depending on age of patient. Adult: IgG<7.51 g/l; IgA<0.82 g/l; IgM<0.46 g/l
Full blood countLymphocyte or granulocyte deficit
Neutrophil antibody and function test, challenge with common humoral bacterial antigensResult suggestive of antibody presence or impaired function
Secondary: lung transplant patients, patients under immunosuppressive therapy, HIVIgG and subclasses, IgA, IgMDecreased values, depending on age of patient
HIV testingPositive HIV serology
ABPAAsthma, wheezing, coughing up brownish mucoid plugs or blood, upper lobe predominanceTotal IgE, sputum sampleRaised total IgE>1000 ng/ml, presence in sputum
Specific serum IgE and IgG to Aspergillus fumigatusRaised Aspergillus IgE and/or IgG
Aspergillus fumigatus skin prick testPositive skin prick test
Rheumatic disorders (RA, SLE, Sjögren, ankylosing spondylitis, relapsing polychondritis)RA: rheumatoid nodule, arthritis, synovitis, specific skeletal deformities, rheumatoid nodule, other skin symptoms, etcAutoimmune screening: rheumatoid factor, ANCAs, ANAs and anti-citrullinated peptide antibodiesDiagnosis depending on clinical examination combined with autoimmune screening results (positivity of rheumatoid factor, anti-citrullinated peptide antibodies, ANCAs, ANAs and/or ANA subtypes)
SLE: malar rash, ulcers, neuropsychiatric symptoms, etcRheumatological advice
COPDDyspnoea, Smoking history, Recurrent infectionsSpirometry, bronchodilatation testObstructive lung function
Traction, obstruction, inhalationSarcoïdosis: fatigue, erythema nodosum, lupus pernio, arthralgia, uveitis, Bell's palsy, etcChest CT scanHilar lymphadenopathy, reticulonodular infiltrates, pulmonary infiltrates, fibrocystic or bullous changes, non-caseating granulomas, upper lobe predominance
History of radiation therapyBiopsy
History of inhalation/aspiration traumaBronchoscopy if imaging showing foreign body
YNS, Young's syndrome, amyloidosis, endometriosisYNS: yellow dystrophic nails, lymphoedema, sinusitis, pleural effusionExclusion diagnosis based on imaging and clinical findings
Young's syndrome: history of mercury contact, rhinosinusitis, infertilityUrological advice
Endometriosis: pelvic pain, infertility, cyclic haemoptysis/painGynaecological evaluation
IdiopathicLower lobe predominance, combined chronic rhinitis/sinusitisAll of the above excludedExclusion diagnosis
  • ABPA, allergic brochopulmonary aspergillosis; ANA, anti-nuclear antibodies; ANCA, anti-neutrophil cytoplasmic antibodies; CFTR, cystic fibrosis transmembrane conductance regulator; COPD, chronic obstructive pulmonary disease; IBD, inflammatory bowel disease; NPD, nasal potential difference; RA, rheumatoid arthritis; SLE, systemic lupus erythematosus; tTG antibodies, tissue transglutaminase antibodies; YNS, yellow nail syndrome.