Tuberculosis with normal
or minimal change of Chest Radiograph,
culture-positive for Mycobacterium tuberculosis
Many patients require the outpatient services due to having cough for a long time (over 3 weeks). Most of them have the normal chest radiograph (CXR) or have the manifestations of the fibrosis or calcification in the past. Base on the principle that we have to examine the sputum (acid-fast smear and culture 3 sets) if someone have cough more than three weeks, if some patients’ smear are positive or culture positive, we need one more PCR examination to confirm. Only having done these examinations, we can make the diagnosis for pulmonary tuberculosis (TB) and then inform the national organization. Although most of patients can accept this medical procedure, some patients still refuse this kind of treatment and have no insight. These behaviors perplex the care-providers, public health practitioners and observers. Our article emphasizes the topic about some pulmonary tuberculosis patients with normal chest radiography but culture positive.
To diagnose the illness as pulmonary tuberculosis, we have to integrate three clinical examinations: clinical symptoms, chest radiograph and sputum examination. Generally speaking, the majority has abnormal finding on chest radiograph, but there still are some patients (1~10%) having normal chest radiograph. If we did not add sputum examination to confirm, this omission may worsen this disease. Most important of all, we have to pay more attention on the patient who have coughed for a long time or have the contact history to pulmonary tuberculosis.
Besides asking the patient whether he had the symptom of cough, fever, fatigue or poor appetite, we have to consider the possibilities that patients have the contact history of TB, or the history of TB, and how is the curative effect in the past.
Chest radiograph is the simplest and valuable examination, but we can not infer the activity of Mycobacterium tuberculosis just according to one time of examination. We have to compare with the past radiograph to make a proper inference. Generally speaking, most of the chest radiography manifests fibrotic nodule or calcified focus, and it was regarded as old inactive pulmonary tuberculosis. However, recent study reports 5 % of CXR calcification and fibrotic foci are active pulmonary tuberculosis, moreover, it also stands the reason why we miss the diagnosis easily.
Acid-fast smear is convenient and rapid. If we add the PCR examination, we could find out the possibility of the pulmonary tuberculosis in the early stage and treat it timely. Certainly, culture for Mycobacterium tuberculosis still is the standard examination, but it takes too much time (about 1~2 months) and have to exclude the false-positive in lab.
On 2008, Dr. Pepper published an article at IJTLD (International Journal of Tuberculosis and Lung Disease). Of 601 study patients with normal chest radiograph, there are 53 persons (9%) having culture-positive sputum, 22 percentages have HIV positive and the other 5 percent persons have HIV negative. Other articles also confirm that pulmonary tuberculosis patients with HIV positive are almost 11% having normal chest radiograph. In IJTLD 1998, Dr. Harries published an article that among 79 patients with negative smears and normal CXR, or someone who is minimally suspected of tuberculosis, followed up over 3 months with repeat sputum smears and chest radiography. In his study, of 16 persons were culture-positive for Mycobacterium tuberculosis, 7 persons developed a TB-CXR. Of 41 cultures-negative patients, 13 persons developed a TB-CXR, including one patient who became sputum smear positive. Therefore, to prevent the aggravation of this disease, we have to remedy the culture-positive patients as soon as possible. Furthermore, in Chest 1999, Dr. Mirciniuk described the early diagnosis of pulmonary tuberculosis when the chest radiograph (CXR) is normal. Identified from a review of 518 conservative patients with culture-positive pulmonary TB, there are 25 persons having normal CXR, but 23 of the 25 patients were symptomatic at the time of diagnosis, with cough over 1 month or fever over 1 week. Skin-test conversions after contacting with the infectious TB, 11 patients were identified because of contact tracing from cases of infectious pulmonary TB. According to the incidence on different years, the incidence 0.7% (1988 to 1989) and 3.5% (1990 to 1991) were increased to 10% (1996 to 1997). Although the incidence of the HIV infection or
the population of the immigrant has increased, we can not ignore the progress of the lab technique.
The population of the patient with culture-positive and normal chest radiograph is not the less. Moreover, to exclude the occurrence of the false positive, our hospital suggests taking further examination (computed tomography and bronchoscope). Our hospital looks forward to locate the accurate nidus with proper examination, especially for someone who has contact history with pulmonary TB, long-time cough or weak resistance. To prevent the spread of Mycobacterium tuberculosis, we have to examine this kind of patient actively and make a proper diagnosis for treatment.