What if AFB smear is negative?
A negative AFB smear may mean that no infection is present, that symptoms are caused by something other than mycobacteria, or that the mycobacteria were not present in sufficient numbers to be seen under the microscope. Usually three samples are collected to increase the probability that the organisms will be detected.
What is smear negative pulmonary TB?
Abstract. Diagnostic difficulties arise when sputum smears are negative for acid-fast bacilli in tuberculin-positive patients with compatible symptoms and chest radiographs for tuberculosis. Many of these smear-negative patients yield positive cultures for M tuberculosis, whereas others remain culturally negative.
Can chest xray detect TB?
The diagnosis of TB cannot be made by a chest x-ray alone. It can also not be excluded by a chest x-ray. Instead,the diagnosis of active tuberculosis means finding the bacterium in a sample of bodily fluid from the patient.
What does a chest xray show if you have TB?
On a chest x-ray from someone with TB you can often see the cavitation that the TB bacteria form in the lung tissue. The picture here shows a chest x-ray, and the arrow points to a TB cavity in the right upper part of the lung (in an x-ray, the right and left side are reversed).
What does TB look like on a chest xray?
Chest X-ray of a person with advanced tuberculosis: Infection in both lungs is marked by white arrow-heads, and the formation of a cavity is marked by black arrows.
Can a patient with smear negative tuberculosis transmit tuberculosis?
Patients with sputum smear–negative TB are less infectious than patients with sputum smear–positive TB [1, 2]. Nevertheless, patients with smear-negative, culture-positive pulmonary TB are capable of transmitting M. tuberculosis [3, 4].
When to report positive TB smear or culture?
Culture examinations should be completed on all specimens, regardless of AFB smear results. Laboratories should report positive results on smears and cultures within 24 hours by telephone or fax to the primary health care provider and to the state or local TB control program, as required by law. 6.
Can a person with PTB have sputum smear negative?
Those found to have sputum smear negative for AFB and who consented were enrolled into the study. A chest x-ray was ordered for those who were found to be HIV positive. If the chest x-ray results were abnormal, the patient was considered to have sputum smear negative PTB, and started on anti-TB medications.
How does an acid fast smear tell if you have tuberculosis?
The presence of acid-fast-bacilli (AFB) on a sputum smear or other specimen often indicates TB disease. Acid-fast microscopy is easy and quick, but it does not confirm a diagnosis of TB because some acid-fast-bacilli are not M. tuberculosis. Therefore, a culture is done on all initial samples to confirm the diagnosis.