From the lung apices to the hemi-diaphragms, 1.5-mm thick sections were taken at 10-mm intervals. The images were prospectively reconstructed with the use of a high-resolution bone algorithm in diagnosing the lung lesions. The HRCT results were then compared with the results of clinical and para-clinical work-up on the patients. The analysis and comparison of rank values were performed using the chi-square P-values less than 0.05, and the sensitivity, specificity, positive and negative predictive value were likewise computed.
Results showed that 61 of the patients were negative for sputum smear and culture, 9 were positive for both, 5 negative for sputum smear and culture positive and 27 diagnosed according to BAL and TBLB results (Martin and Lazarus 2000, Karam). All of the patients had x-ray or chest radiographs suggesting active PTB through infiltration or cavitation in the upper lobes. HRCT findings concluded that 76 of the patients or 74.5% had active PTB who required work-up confirmation and established a strong positive correlation. The sensitivity of HRCT was placed at a high 96%. Binomial tests were also performed between the final diagnosis and each characteristic "tree-in-bud" and centrilobular appearances radiologic manifestation in determining the diagnostic yield of each characteristic radiologic manifestation obtained from the CT scan. Analysis revealed that neither was individually diagnostic, but their combination accurately confirmed a diagnosis of PTB (Martin and Lazarus, Karam).
Radiography or x-ray in conjunction with skin testing is the standard initial screening method not only when results seem unreliable, the skin test reading is impractical or when there are significant risks of transmission in undiagnosed cases as in institutional settings, like hospitals, jails and long-term facilities (Leung 1999).
Post-primary TB is usually a disease of adolescents and adults, the earliest findings being a heterogeneous, poorly marginated opacity in the apical or posterior portion of the upper lobes. In 40% of cases, chest x-rays revealed cavitation, particularly in cases complicated with extensive fibrosis and structural distortion (Martin and Lazarus 2000, Karam). The most common complication of tuberculous cavitation is endobronchial spread, which is radiographically detectable at 19% but up to 98% by HRCT. In some cases, HRCT may detect indicators of active disease not intercepted or captured by chest radiographs. The higher level of sensitivity of the HRCT may lead to prompt and accurate diagnosis even while microbiology results are pending.
Treatment - Latent tuberculosis infection is usually indicated, whatever the patient's age and for patients who belong to the high-risk groups. There are no standard recommendations for patients in the lower-risk groups but health care workers weigh the benefits against the risks, especially for patients older than 35 (Jerant 2000). Pregnant women with PTB are usually subjected to treatment until after delivery, but those belonging to the high-risk groups or recently infected are often given isoniazid as soon as the active disease is excluded (Jerant). Usual dosage is 5-300 mg isoniazid per kilogram body weight a day for nine months. The nine-month program is preferred to the previous six months' treatment schedule on account of the findings of randomized trials among HIV / AIDS-negative patients. The findings showed that treatment for 9 months was more effective than 6 months. A regimen of 12 months also showed minimal benefit. A twice weekly dosage also seemed acceptable when compliance with the daily dosage becomes difficult or questionable.
The nine-month treatment regimen already has stated advantages, but the six-month regimen exhibited protection and appeared superior in certain tests, which used placebo in HIV / AIDS-negative and HIV / AIDS-positive patients (Jerant 2000). In view of the wide variations of patient responses and compliance and local health department resources, health authorities recommend the six-month instead of the nine-month regimen if the six-month treatment would produce more favorable outcomes and prove more cost-effective. These authorities and the American Academy of Pediatrics, however, stress on the nine-month duration of treatment for children. Pyridoxine or hexa-betalin is often prescribed at a dosage of 10-50 mg a day to reduce the likelihood of drug-related peripheral neuropathy with the use of isoniazid for all children six years and older. Pyridoxine is likewise advised for patients with neuropathic conditions, such as diabetes, alcoholism and malnutrition, pregnancy and for patients on anticonvulsant therapy.
Patients taking isoniazid must undergo monthly clinical evaluations for latent tuberculosis infection (Jerant 2000). They can choose a one-month supply of medication at a time. If they work, they can take advantage of office mechanisms that would track them down and arrange for follow-up visits. In each visit, they should be evaluated for signs and symptoms of anemia, hepatitis and neurotoxicity. They should also be informed about and educated on these symptoms and to stop taking the medicines when such symptoms occur.
A four-drug regimen is initiated in treating adults with confirmed or suspected active tuberculosis (Jerant 2000). After two months, they should continue taking isoniazid and rifampicin alone if repeat sputum tests are negative and the patients show clinical improvements. They should maintain the regimen for another four months and then discontinue if the sputum test findings remain negative. A physician should conduct monthly evaluations of the patients' smears and cultures throughout treatment.
Health authorities recommend that HIV / AIDS patients who catch active TB should include streptomycin-based medications in their regimens or regimens that use rifampin or rifabutin as substitutes (Jerant 2000). These regimens do not require the discontinuation or avoidance of protease inhibitors and non-nucleoside reverse transcriptase inhibitors. The dosage and duration can be made flexible, depending on the patients' clinical response.
There are patients who develop or catch multi-drug resistant TB as a consequence of the inappropriate use of medications or the prescription of inadequate regimens that can favor the proliferation or spread of M. tuberculosis strains with drug-resistant mutations (Jerant 2000). When this happens, the drug responsible should be identified and an appropriate alternative chemotherapeutic regimen prescribed in its place. Multi-drug resistant TB is a disease that is resistant to, at least, isoniazid and rifampin. The patient should be put on a regimen of 3-4 drugs to which TB is susceptible. The task is challenging, considering the adverse effects of second-line or alternative agents and the frequent need to be on prolonged therapy of between a year and two years. Consultation with an infectious disease or pulmonary specialist may be necessary or ideal in determining the most appropriate treatment for such cases. Surgery may, for example, be the most suitable option in a patient with a well-localized disease and adequate pulmonary reserves.
Children are generally treated the way adults are treated, but streptomycin is preferred to ethambutol in very young children because of the difficulty in monitoring for ocular toxicity (Jerant 2000). Pregnant women with active TB should continue taking anti-tuberculous medications if these have been started prior to pregnancy. These medications should include isoniazid, rifampin, ethambutol and pyridoxine. These patients should not use pyrazinamide, streptomycin, kanamycin, capreomycin, quinolones, ethionamide and cycloserine.
Bureau of Tuberculosis Control. Identifying and Treating "Old Tuberculosis." TB Fact Sheet 3c. New York City Department of Health and Mental Hygiene, December 28, 2004. http://www.ci.nyc.ny.us/html/doh/html/tb/tb3c.html
Harisinghani, Mukesh. Tuberculosis from Head to Toe. Radiological Society of North America, 2000. http://radiographics.rsnajnls.org/cgi/content/abstract/20/2/449
Karam, bakhashayesh, et al. Role of HRCT in Diagnosing Active Pulmonary Tuberculosis. National Research Institute of Tuberculosis and Lung Disease, Academy of Medical Sciences of Iran. Iran: Maseeh Daneshvary Hospital. http://www.ams.ae.ir/AIM/0031/karam0031.html
Kirchner, Jeffrey T. Detection of Tuberculosis Despite Normal Chest Findings. American Family Physicians, July 1999. http://www.aafp.org/afp/990700ap/tips.html#Detection