Predictors of non-cystic fibrosis bronchiectasis in Indigenous adult residents of central Australia: results of a case–control study

Data are presented as n or mean±sd, unless otherwise stated. PBL: peripheral blood leukocyte. Combined radiological scores for all lobes for cases with HTLV-1 for which no alternative cause of bronchiectasis was found. Each lobe was scored separately by radiologists blinded to HTLV-1 status (see Methods). The lingular segment of the left upper lobe was regarded as a separate lobe. One case (HTLV-1 PVL 242 copies per 10⁵ PBLs) for which high-resolution computed tomography was not available for review was not included in this analysis. 10 cases with alternative causes were excluded (severe pneumonia n=5; empyema n=2; pulmonary abscess n=1; pulmonary tuberculosis n=1; severe childhood bronchiolitis n=1). ^#: rank-sum test; ^¶: a composite score comprising those for all other radiological parameters (bronchiectasis, bronchial wall thickening, cystic bronchiectasis, saccular bronchiectasis, mucus plugging/centrilobular nodules and ground-glass opacities).

LRTI: lower respiratory tract infection; ICU: intensive care unit; HTLV-1: human T-cell leukaemia virus type 1; PVL: pro-viral load; NTM: nontuberculous mycobacteria. ^#: risk of bronchiectasis per 5 years. ^¶: residence >80 km from Alice Springs documented in medical records. ⁺: admitted with any non-severe LRTI prior to diagnosis (cases) or date of recruitment (controls). ^§: number of admissions with LRTIs prior to diagnosis (cases) or date of recruitment (controls). ^ƒ: number of ICU admissions for LRTI in childhood and adulthood combined prior to diagnosis for cases or to date of recruitment for controls. ^##: severe pneumonia (n=16), severe bronchiolitis (n=4) and pulmonary tuberculosis (n=1) at any age (see Methods); includes one case with combined IgA and IgG deficiency; three controls had severe LRTI (pulmonary tuberculosis n=1, pulmonary abscess n=1, severe pneumonia n=1). ^¶¶: HTLV-1 Western blot or HTLV-1c PCR positive. ⁺⁺: low HTLV-1 PVL, <1000 copies per 10⁵ peripheral blood leukocytes (PBLs); high HTLV-1 PVL, ≥1000 copies per 10⁵ PBLs. ^§§: the number of pathogens isolated divided by the number of sputum samples collected, calculated once for each admission. ^ƒƒ: NTM isolated from six cases prior to diagnosis included 1) a novel species that could not be identified together with a scotochromogenic mycobacterium, 2) Mycobacterium avium complex in a patient with pulmonary tuberculosis and 3) Mycobacterium simiae (isolated once from one case and twice from another); mycobacteria were not identified to species level in two cases and one control from which an NTM was isolated only once. ^###: eosinophilia recorded on at least two occasions 12 months apart (prior to diagnosis for cases). ^¶¶¶: Strongyloides seropositive or larvae identified in stool at any time prior to date of recruitment. ⁺⁺⁺: infective dermatitis recorded in case notes (cases HTLV-1⁺ n=10, HTLV-1⁻ n=2; controls HTLV-1⁺ n=1, HTLV-1⁻ n=5). ^§§§: clinical diagnosis of scabies recorded in case notes (no case diagnosed by microscopy). ^ƒƒƒ: any history of tobacco smoking recorded in case notes. ^####: any history of harmful alcohol consumption recorded in case notes.

LRTI: lower respiratory tract infection; PVL: pro-viral load; NTM: nontuberculous mycobacteria. ^#: risk of bronchiectasis per 5 years. ^¶: residence >80 km from Alice Springs in adulthood. ⁺: admitted with any non-severe LRTI prior to diagnosis (cases) or date of recruitment (controls). ^§: number of LRTI admissions prior to diagnosis (cases) or date of recruitment (controls). ^ƒ: severe pneumonia (n=8), severe bronchiolitis (n=1), and pulmonary tuberculosis (n=1) at any age (see Methods); three controls with HTLV-1 had a severe LRTI (pulmonary tuberculosis n=1, pulmonary abscess n=1, severe pneumonia n=1). ^##: odds of bronchiectasis per 100 unit increase in HTLV-1 copies per 10⁵ peripheral blood leukocytes (PBLs). ^¶¶: low HTLV-1 PVL, <1000 copies per 10⁵ PBLs; high HTLV-1 PVL, ≥1000 copies per 10⁵ PBLs. ⁺⁺: the number of pathogens isolated divided by the number of sputum samples collected, calculated once for each admission. ^§§: NTM isolated from four cases prior to diagnosis included 1) Mycobacterium avium complex in a patient with pulmonary TB and 2) Mycobacterium simiae (isolated twice); NTM were not identified to species level in two cases from which an NTM was isolated only once. ^ƒƒ: peripheral blood eosinophilia recorded on at least two occasions 12 months apart (prior to diagnosis for cases). ^###: Strongyloides seropositive or larvae identified in stool at any time prior to date of recruitment (cases n=18 (Strongyloides seropositive n=18, larvae in stool n=0); controls n=6 (Strongyloides seropositive n=5, larvae in stool n=1)). ^¶¶¶: infective dermatitis recorded in case notes (cases HTLV-1⁺ n=10, HTLV-1⁻ n=2; controls HTLV-1⁺ n=1, HTLV-1⁻ n=5). ⁺⁺⁺: clinical diagnosis of scabies recorded in case notes (no case diagnosed by microscopy). ^§§§: any history of tobacco smoking recorded in case notes. ^ƒƒƒ: any history of harmful alcohol consumption recorded in case notes.