tuberculosis diagnosis tuberculosis diagnosis tuberculosis is diagnosed by finding mycobacterium tuberculosis bacteria in a clinical specimen taken from the patient. while other investigations may strongly suggest tuberculosis as the diagnosis, they cannot confirm it. for an overview of the disease, see tuberculosis. tuberculosis diagnosism. tuberculosis (stained red) in sputumpurposediagnosed by finding mycobacterium tuberculosis a complete medical evaluation for tuberculosis (tb) must include a medical history, a physical examination, a chest x-ray and microbiological examination (of sputum or some other appropriate sample). it may also include a tuberculin skin test, other scans and x-rays, surgical biopsy. medical history the medical history includes obtaining the symptoms of pulmonary tb: productive, prolonged cough of three or more weeks, chest pain, and hemoptysis. systemic symptoms include low grade remittent fever, chills, night sweats, appetite loss, weight loss, easy fatiguability, and production of sputum that starts out mucoid but changes to purulent. other parts of the medical history include prior tb exposure, infection or disease and medical conditions that increase risk for tb disease such as hiv infection. depending on the sort of patient population surveyed, as few as 20%, or as many as 75% of pulmonary tuberculosis cases may be without symptoms. tuberculosis should be suspected when a pneumonia-like illness has persisted longer than three weeks, or when a respiratory illness in an otherwise healthy individual does not respond to regular antibiotics. physical examination a physical examination is done to assess the patient's general health. it cannot be used to confirm or rule out tb. however, certain findings are suggestive of tb. for example, blood in the sputum, significant weight loss and drenching night sweats may be due to tb. microbiological studies lab findingsdistinctive clusters of colorless mycobacterium tuberculosis form in this culture.gram+shaperods a definitive diagnosis of tuberculosis can only be made by culturing mycobacterium tuberculosis organisms from a specimen taken from the patient (most often sputum, but may also include pus, csf, biopsied tissue, etc.). a diagnosis made other than by culture may only be classified as "probable" or "presumed". for a diagnosis negating the possibility of tuberculosis infection, most protocols require that two separate cultures both test negative. sputum sputum smears and cultures should be done for acid-fast bacilli if the patient is producing sputum. the preferred method for this is fluorescence microscopy (auramine-rhodamine staining), which is more sensitive than conventional ziehl–neelsen staining. in cases where there is no spontaneous sputum production, a sample can be induced, usually by inhalation of a nebulized saline or saline with bronchodilator solution. a comparative study found that inducing three sputum samples is more sensitive than three gastric washings. alternative sampling in patients incapable of producing a sputum sample, common alternative sample sources for diagnosing pulmonary tuberculosis include gastric washings, laryngeal swab, bronchoscopy (with bronchoalveolar lavage, bronchial washings, and/or transbronchial biopsy), and fine needle aspiration (transtracheal or transbronchial). in some cases, a more invasive technique is necessary, including tissue biopsy during mediastinoscopy or thoracoscopy. pcr other mycobacteria are also acid-fast. if the smear is positive, pcr or gene probe tests can distinguish m. tuberculosis from other mycobacteria. even if sputum smear is negative, tuberculosis must be considered and is only excluded after negative cultures. other many types of cultures are available. traditionally, cultures have used the löwenstein-jensen (lj), kirchner, or middlebrook media (7h9, 7h10, and 7h11). a culture of the afb can distinguish the various forms of mycobacteria, although results from this may take four to eight weeks for a conclusive answer. new automated systems that are faster include the mb/bact, bactec 9000, versatrek, and the mycobacterial growth indicator tube (mgit). the microscopic observation drug susceptibility assay culture may be a faster and more accurate method. pulmonary tuberculosis characterized by granulomatous inflammation with necrotizing epithelioid granulomas. low power view. h&e stain. pulmonary tuberculosis featuring necrotizing granulomas, h&e stain. pulmonary tuberculosis featuring necrotizing granulomas, high power view, h&e stain. acid fast bacilli, ziehl–neelsen stain. radiography main article: tuberculosis radiology chest x-ray and ct tuberculosis creates cavities visible in x-rays like this one in the patient's right upper lobe. ct scan of peritoneal tuberculosis, a form of extrapulmonary tuberculosis. the omentum and peritoneal surfaces are thickened (arrows). in active pulmonary tb, infiltrates or consolidations and/or cavities are often seen in the upper lungs with or without mediastinal or hilar lymphadenopathy or pleural effusions ( tuberculous pleurisy). however, lesions may appear anywhere in the lungs. in disseminated tb a pattern of many tiny nodules throughout the lung fields is common - the so-called miliary tb. in hiv and other immunosuppressed persons, any abnormality may indicate tb or the chest x-ray may even appear entirely normal. abnormalities on chest radiographs may be suggestive of, but are not necessarily diagnostic of, tb. however, chest radiographs may be used to rule out the possibility of pulmonary tb in a person who has a positive reaction to the tuberculin skin test and no symptoms of the disease. cavitation or consolidation of the apexes of the upper lobes of the lung or the tree-in-bud sign may be visible on an affected patient's chest x-ray. the tree-in-bud sign may appear on the chest cts of some patients affected by tuberculosis, but it is not specific to tuberculosis. fdg pet/ct fdg pet/ct can play several useful roles in patients with confirmed or suspected tb. these roles include detection of active tb lesions, assessment of disease activity, differentiation between active and latent disease, assessment of disease extent (staging), monitoring response to treatment, and identification of potential biopsy target. abreugraphy further information: abreugraphy a variant of the chest x-ray, abreugraphy (from the name of its inventor, dr. manuel dias de abreu) was a small radiographic image, also called miniature mass radiography (mmr) or miniature chest radiograph. though its resolution is limited (it doesn't allow the diagnosis of lung cancer, for example) it is sufficiently accurate for diagnosis of tuberculosis. much less expensive than traditional x-ray, mmr was quickly adopted and extensively utilized in some countries, in the 1950s. for example, in brazil and in japan, tuberculosis prevention laws went into effect, obligating ca. 60% of the population to undergo mmr screening. the procedure went out of favor, as the incidence of tuberculosis dramatically decreased, but is still used in certain situations, such as the screening of prisoners and immigration applicants. immunological test als assay for an overview of als assay, see antibodies from lymphocyte secretions. antibodies from lymphocyte secretion or antibody in lymphocyte supernatant or als assay is an immunological assay to detect active diseases like tuberculosis, cholera, typhoid etc. recently, als assay nods the scientific community as it is rapidly used for diagnosis of tuberculosis. the principle is based on the secretion of antibody from in vivo activated plasma b cells found in blood circulation for a short period of time in response to tb-antigens during active tb infection rather than latent tb infection. transdermal patch a similar approach to the als assay. the transdermal patch is a suggested method of detecting active m.tuberculosis circulating within blood vessels of patient. this skin patch contains antibodies recognizing the secreted bacterial protein mpb-64 passing through the blood capillaries of the skin creating an immunological response. if the patch detects this secreted bacterial protein, the surrounding skin will redden. tuberculin skin test further information: tuberculin skin test two tests are available: the mantoux and heaf tests. mantoux skin test further information: mantoux test injecting a mantoux skin test the mantoux test for tb involves intradermally injecting ppd (purified protein derivative) tuberculin and measuring the size of induration 48-72 hours later. the mantoux skin test is used in the united states and is endorsed by the american thoracic society and centers for disease control and prevention (cdc). if a person has had a history of a positive tuberculin skin test, another skin test is not needed. heaf test further information: heaf test the heaf test was used in the united kingdom until 2005, and is graded on a four-point scale. the mantoux test is now used. the equivalent mantoux test positive levels done with 10 tu (0.1 ml 100 tu/ml, 1:1000) are 0–4 mm induration (heaf 0 to 1) 5–14 mm induration (heaf 2) greater than 15 mm induration (heaf 3 to 5) cdc classification of tuberculin reaction an induration (palpable raised hardened area of skin) of more than 5–15 mm (depending upon the person's risk factors) to 10 mantoux units is considered a positive result, indicating tb infection. 5 mm or more is positive in hiv-positive person recent contacts of tb case persons with nodular or fibrotic changes on cxr consistent with old healed tb patients with organ transplants and other immunosuppressed patients 10 mm or more is positive in recent arrivals (less than 5 years) from high-prevalent countries injection drug users residents and employees of high-risk congregate settings (e.g., prisons, nursing homes, hospitals, homeless shelters, etc.) mycobacteriology lab personnel persons with clinical conditions that place them at high risk (e.g., diabetes, prolonged corticosteroid therapy, leukemia, end-stage renal disease, chronic malabsorption syndromes, low body weight, etc.) children less than 4 years of age, or children and adolescents exposed to adults in high-risk categories 15 mm or more is positive in persons with no known risk factors for tb (note: targeted skin testing programs should only be conducted among high-risk groups) a tuberculin test conversion is defined as an increase of 10 mm or more within a 2-year period, regardless of age. bcg vaccine and tuberculin skin test there is disagreement on the use of the mantoux test on people who have been immunized with bcg. the us recommendation is that in administering and interpreting the mantoux test, previous bcg vaccination should be ignored; the uk recommendation is that interferon-γ tests should be used to help interpret positive tuberculin tests, also, the uk does not recommend serial tuberculin skin testing in people who have had bcg (a key part of the us strategy). in their guidelines on the use of quantiferon gold the us centers for disease control and prevention state that whereas quantiferon gold is not affected by bcg inoculation tuberculin tests can be affected. in general the us approach is likely to result in more false positives and more unnecessary treatment with potentially toxic drugs; the uk approach is as sensitive in theory and should also be more specific, because of the use of interferon-γ tests. under the us recommendations, diagnosis and treatment of latent tuberculosis infection (ltbi) is considered for any bcg-vaccinated person whose skin test is 10 mm or greater, if any of these circumstances are present: was in contact with another person with infectious tb was born or has resided in a high tb prevalence country is continually exposed to populations where tb prevalence is high. these have been reviewed in detail. adenosine deaminase in 2007, a systematic review of adenosine deaminase by the nhs health technology assessment programme concluded "there is no evidence to support the use of ada tests for the diagnosis of pulmonary tb. however, there is considerable evidence to support their use in pleural fluid samples for diagnosis of pleural tb, where sensitivity was very high, and to a slightly lesser extent for tb meningitis. in both pleural tb and tb meningitis, ada tests had higher sensitivity than any other tests." nucleic acid amplification tests (naat) naats for tb are a heterogeneous group of tests that use either the polymerase chain reaction (pcr) technique or transcription-mediated amplification (tma) or other forms of nucleic acid amplification methods to detect mycobacterial nucleic acid. these tests vary in which nucleic acid sequence they detect and vary in their accuracy. in the decade of the 2000s, the two most common commercially available tests were the amplified mycobacterium tuberculosis direct test (mtd, gen-probe) and amplicor (roche diagnostics). in 2007, a systematic review of naat by the nhs health technology assessment programme concluded that "naat test accuracy to be far superior when applied to respiratory samples as opposed to other specimens. although the results were not statistically significant, the amtd test appears to perform better than other currently available commercial tests." xpert ® mtb/rif and xpert mtb/rif ultra has high specificity in diagnosing extrapulmonary tuberculosis and is accurate in detecting rifampicin resistance. however, clinicians should rely on clinical judgement to diagnose tb meningitis when culture results are negative. a 2007 before-after observational study found that use