Can Primary Care MDs Manage TB?
Source: LoBue PA, et al. Int J Tuberc Lung Dis. 2001;5:933-938.
Community physicians are at the front lines in the battle against tuberculosis (TB). They are often the first to recognize (or not) cases of active TB, and often provide the initial diagnostic evaluation and management. In San Diego County, where 319 cases of active TB were diagnosed in 1997, two thirds (65%) of the cases were managed by community physicians. San Diego represents a county with a fairly high caseload of TB, ~12% of which was INH resistant and ~1% was multi-drug resistant at that time.
To investigate the knowledge and practices of clinicians in the community caring for patients with latent or active TB, researchers at UCSD and the San Diego County Public Health Department distributed a survey to each of 384 physicians who had reported at least one TB case to the PHD in the years 1995 to 1997. The survey addressed basic questions regarding the diagnosis and management of patients with latent or active TB. A total of 150 physicians (39%) responded. Of these, 77% had been trained in the United States; 38% were infectious disease or pulmonary medicine specialists, internists (47%), family practitioners (21%), pediatricians (14%), or other (11%). Their experience in the management of patients with TB during the previous 2 years varied from 0-5 patients (59%), 6-10 (24%), or 11 or more (17%).
When compared with current practice guidelines, the number of correct responses was pretty good at 83%, although the accuracy of the responses varied widely (51-94%) and there were some glaring deficiencies: 1) 22% of physicians believed that 3 negative AFB sputum smears excluded a diagnosis of pulmonary TB (one hopes they misread the question!). Sputum smears are able to detect only 50-60% of active TB cases; 2) 11% believed that a negative CXR ruled out a diagnosis of active pulmonary TB; 3) 24% failed to recognize the minimum duration of treatment for active TB (6 months); 4) 49% failed to recognize a positive TST in patients with an abnormal CXR consistent with active or healed TB (5 mm); 5) 36% failed to correctly identify a positive TST in a patient with close contact with an active TB case (5 mm). Specialists and physicians trained in the U.S., were more likely to indicate correct responses, as were physicians with a greater level of experience (3 or more cases per year). Although the number of physicians responding to the survey was low, suggesting the survey results may not be entirely representative of the larger treating community, it nevertheless points out the continuing need for provider education in the management of latent and active TB. It also provides continued justification for the ongoing public health management and physician supervision of all reported TB cases. Although this is a relatively labor intensive public health measure, the need continues to outweigh the cost.
SV-40 in Non-Hodgkins Lymphoma
Sources: Vilchez R, et al. Lancet. 2002;359:817-823; Shivapurkar N, et al. Lancet. 2002;359:851-852.
The role of simian virus 40 (sv-40) in the development of "soft cell" cancers, such as sarcomas, certain lung and brain cancers, and lymphoma has long been debated. While some evidence suggests that the incidence of these cancers is not increasing, other data suggest that non-Hodgkin’s lymphomas (NHL) is on the increase, possibly the result of an ever-aging population. Between 1955 and 1963, the early polio vaccines were produced using green monkey kidney cells. As a result, some believe that these early batches of vaccine, which were administered to possibly as many as 30 million people, may have been contaminated with SV-40.
Polyomaviruses, such as SV-40, JC virus, and BK virus, are generally species-specific, although JC and BK virus are 70% homologous with SV-40 virus, and viruses antigenically similar to SV-40 have been found in people with progressive multifocal leukoencephalopathy (SV-40-like-PML viruses). These viruses may also have the potential to transmogrity normal cells into cells with malignant potential. For example, experiments in transgenic mice suggest that the gene responsible for a regulatory protein of JC virus replication, called T-antigen, is oncogenic, and specific DNA sequences of JC virus T-antigen have been found in medulloblastoma cells in children (Kemper, CA. Infectious Disease Alert. 1999;17:136).
In these reports above, 2 independent laboratories detected a similar frequency of SV-40 antigen sequences in cells of NHL patients. In one study, specimens obtained from 68 patients with NHL were compared with tissues from hundreds of other tumors and 40 healthy "control" specimens. Using molecular techniques, DNA sequences corresponding to SV-40 T-antigen were found in 43% of NHL cells, compared with fewer than 10% of other tumor cells and none of the cells from healthy individuals. The other study found that 42% of cells from 150 NHL tumors tested positive compared with 186 negative nonmalignant control specimens. Sequences of other polyoma viruses were not detected. While no data regarding polio vaccine history for these viral "footprints" in human malignant cells will continue to be debated.
Dr. Kemper, Clinical Associate Professor of Medicine, Stanford University, Division of Infectious Diseases; Santa Clara Valley Medical Center, is Associate Editor of Infectious Disease Alert.
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