Guidelines on the Prevention and Control of Tuberculosis in Ireland

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<strong>Guidelines</strong> on the Prevention and Control of Tuberculosis in Ireland 2010HSE/HPSCThe following radiographic findings are commonly believed to represent latent/inactive TB. Whilesome are associated with increased risk of reactivation of active TB disease in future, others arenot.• Granulomas that may be calcified or not: this doubles the risk of reactivation resulting inactive TB disease• Calcified hilar lymph nodes: if there are no parenchymal lesions, these individuals do notappear to have an increased risk relative to those who are TST positive and have normalchest X-rays• Costophrenic angle blunting: this is due to past pleural effusion or pleurisy which may havemany causes. The most common cause in individuals from countries with high TB incidenceand other TB-endemic areas is previous exposure to Mycobacteria tuberculosis. Suchindividuals have an increased risk of reactivation• Apical pleural capping: this is not considered to be related to TB infection and is a nonspecificfinding that is more common in older individuals• Apical fibronodular disease: this is associated with increased risk of reactivation rangingfrom 6 to 19 times greater than those who are TST positive and have normal chest X-rays.Individuals with more extensive abnormalities have greater risk of disease. 30Source: Canadian Tuberculosis Standards, 6 th Edition. Public Health Agency of Canada, 2007. Reproduced with the permission of theMinister of Public Works and Government Services, 2009. Available at www.phac-aspc.gc.ca/tbpc-latb/pubs/pdf/tbstand07_e.pdfChest X-ray for the diagnosis of TB diseaseChest radiography [posterior-anterior (PA)] 76 is the usual first step in the evaluation of an individual withpulmonary symptoms. Additional views may be ordered at the clinician’s discretion. It is also recommendedthat patients suspected of having extrapulmonary TB have a chest X-ray to rule out pulmonary disease.In all instances, if the chest X-ray results are abnormal (including pleural TB), sputum samples should becollected on 2 to 3 separate days and tested for acid fast bacilli (AFB) (smears) as well as for culture anddrug susceptibilities.The radiological findings usually seen on chest X-ray for both immunocompetent and immunosuppressedadults are outlined below. However, it is important to be aware that chest X-ray has substantial limitationsin the diagnosis of pulmonary TB disease.Typical findings: a triad of classic findings are seen in immunocompetent adultsPosition- apical-posterior segments of upper lobes or superior segment of lower lobes in 90%Volume loss- this is a hallmark of TB disease as a result of its destructive and fibrotic natureCavitation- this is seen at a later stage and depends upon a vigorous immune response. Therefore,it may not be seen in severely immunocompromised individuals.Atypical features:These will be seen in patients with immunocompromising conditions such as HIV infection,diabetes, renal failure or corticosteroid use.Hilar and mediastinal lymphadenopathy, particularly in HIV-infected individualsNon-cavitary infiltrates and lower lobe involvement-23-
<strong>Guidelines</strong> on the Prevention and Control of Tuberculosis in Ireland 2010HSE/HPSCRadiographic signs of complications:Endobronchial spread of disease. TB may spread via airways to the ipsilateral and contralaterallower lobes. This results in irregular poorly defined small nodular shadows which represent acinarshadows. These will slowly enlarge and coalesce to form TB pneumonia, formerly known as“galloping consumption”Pleural effusion can be seen concomitant with pulmonary disease and may represent TBempyemaPneumothorax can rarely occur as a result of erosion of a caseous focus into a bronchus andsimultaneously into the pleural space causing a bronchopleural fistula.Source: Canadian Tuberculosis Standards, 6 th Edition. Public Health Agency of Canada, 2007. Reproduced with the permission of theMinister of Public Works and Government Services, 2009. Available at www.phac-aspc.gc.ca/tbpc-latb/pubs/pdf/tbstand07_e.pdfLimitations of chest radiographySensitivity: chest radiography will have a sensitivity of only 70% to 80% for diagnosis of activeTB based on the abnormalities listed above. If any abnormality is considered it will have morethan 95% sensitivity. Approximately 10% of HIV-positive persons or close contacts with activepulmonary disease will have normal X-raysSpecificity is relatively poor, in the range of 60% to 70%. If the sensitivity were improved (anyabnormality considered possible TB), then the specificity would be much lowerInter reader variability: one of the greatest problems with chest X-ray reading is that theinterpretation is highly variable. There is very poor agreement between readers regarding thepresence of cavitation, hilar lymphadenopathy and the likelihood of active disease. 30Source: Canadian Tuberculosis Standards, 6 th Edition. Public Health Agency of Canada, 2007. Reproduced with the permission of theMinister of Public Works and Government Services, 2009. Available at www.phac-aspc.gc.ca/tbpc-latb/pubs/pdf/tbstand07_e.pdfRecommendation:Chest X-ray is not considered the gold standard for the diagnosis of pulmonary TB.Chest X-ray in pregnancyThe decision to perform a chest X-ray on women undergoing evaluation for active TB disease duringpregnancy should be made on a case-by-case basis following discussion between the respiratory physician/infectious disease consultant and the consultant radiologist. A lead shield should be used if a chest X-ray isperformed. 77Chest X-ray in childrenChest X-ray is useful in the diagnosis of TB in children. Children should have an anterior-posterior chestX-ray which should be read by a radiologist experienced in paediatric radiology. A lateral chest X-ray istaken only in certain cases and generally after consultation with a radiologist. In the majority of cases,children with pulmonary TB have chest X-ray changes suggestive of TB. The most common finding ispersistent opacification in the lung in conjunction with enlarged hilar or subcarinal lymph glands. A miliarypattern of opacification in HIV-uninfected children is highly suggestive of TB. Patients with persistent-24-
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Guidelines on the Prevention and Control of Tuberculosis in Ireland

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