Am. J. Respir. Crit. Care Med.,
Volume 157, Number 4, April 1998, 1348-1349
CHEST RADIOGRAPHIC FINDINGS IN PATIENTS WITH
TUBERCULOSIS WITH RECENT OR REMOTE INFECTION
To the Editor :
In their study, Jones and colleagues (1) analyzed the radiographic patterns in patients with recently or remotely acquired tuberculosis. They concluded that the radiographic findings
were similar regardless of the presumed timing of infection,
as determined by restriction fragment length polymorphism
(RFLP) patterns. However, I believe that this study has some
limitations that could have had a significant influence on the
final results.
The authors consider that clustered cases correspond to patients who acquired the infection recently, and nonclustered
cases represent reactivation of tuberculosis acquired in the
past. Although the former consideration may be correct for
most patients, the latter premise may not. Similar RFLP patterns suggest that the source of infection is the same and that
the infection is recent for most of the patients in the cluster.
However, the source case may have developed tuberculosis as
a consequence of reactivation of a remotely acquired infection. To deal with this item, the authors have assumed that
one patient from each cluster had reactivation tuberculosis.
However, as it is not possible to accurately identify these patients, they have been pooled with the recently infected patients. Therefore, such a misclassification of a significant number of patients may have influenced the results.
On the contrary, patients with different RFLP patterns
were considered to have reactivation tuberculosis acquired in
the past. Nevertheless, RFLP only provides information about
the relatedness of cases and does not indicate the timing of infection. In other words, the failure to identify other clustered
cases does not necessarily mean that the infection was remote;
it could have been acquired recently from an individual not included in the present study. In fact, the ethnic diversity of the
patients in the study of Jones and coworkers favors this possibility. Finally, there is some controversy, as yet unresolved,
about the epidemiological interpretation of RFLP patterns,
particularly in cases without temporal relationships (2).
On the other hand, 33 of the 103 patients were known to be
infected with human immunodeficiency virus (HIV). Although in Table 1 the authors presented the results separately,
I believe that HIV-seropositive patients should not be considered for this analysis. As opposed to HIV-seronegative patients, most HIV-infected patients are thought to develop tuberculosis as a result of recent transmission (3, 4). This is
probably due to their greater susceptibility to progressive disease following infection than immunocompetent patients. In
addition, the development of cavities in pulmonary tuberculosis is not a characteristic of the tubercle bacilli, but the result
of the immune response of the host. Consequently, the rate of
cavitary disease typical of reactivation tuberculosis would be
considerably lower in HIV-infected patients although they
had acquired the infection remotely. Moreover, the radiographic features of HIV-infected patients with tuberculosis
do not follow the patterns of immunocompetent patients, the
former having higher rates of lymphadenopathy, pleural effusion, and involvement of lower lobes, and lower rates of cavitary disease and upper lobe involvement (5). Furthermore,
the pattern of chest radiographs in HIV-infected patients varies with the degree of immunosuppression, an aspect not considered in this study, being more "typical" in the earlier stages
of the infection (9).
In summary, the finding of similar chest radiographs in
clustered and unclustered patients, whether HIV-infected or
not, does not necessarily mean that the radiographic features
of recently and remotely acquired tuberculous infection are
similar.
Julio
Collazos
Section of Infectious Diseases
Hospital de Galdakao
Vizcaya, Spain
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Jones, B. E.,
R. Ryu,
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1997.
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[Abstract/Free Full Text].
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From the Authors:
Dr. Collazos points out that RFLP analysis is an imperfect
method for separating tuberculosis patients with disease due
to recent infection from those with disease due to remote infection. Nevertheless, RFLP analysis is widely considered to
be the most reliable marker of recent infection that is currently available. Furthermore, in the patients from Los Angeles we studied, epidemiologic links were found between clustered patients (infected with the same M. tuberculosis strain,
by RFLP analysis), but not between nonclustered patients,
providing strong evidence that clustering is a reliable marker
of recent tuberculosis transmission in this population (1). This
confirms that most patients in our study in large clusters had
tuberculosis from recent infection, whereas most nonclustered
patients had tuberculosis from remote infection.
Dr. Collazos objects to the inclusion of HIV-infected patients in our analysis but provides no substantive reason for
this objection. He states that we did not consider the results of
prior studies showing that chest radiographic findings in HIV-infected patients vary according to the degree of immunodeficiency. As we noted in our discussion (2), this information
supports our conclusion that the chest radiographic appearance probably reflects the integrity of the immune response,
not the timing of tuberculosis infection.
Peter F.
Barnes
Center for Pulmonary and Infections
Disease Control
University of Texas Health Center at
Tyler
Tyler, Texas
1.
Barnes, P. F.,
Z. Yang,
S. Preston-Martin,
J. M. Pogoda,
B. E. Jones,
M. Otaya, et al
.
1997.
Patterns of tuberculosis transmission in central Los
Angeles.
J.A.M.A.
278:
1159-1163
[Abstract/Free Full Text].
2.
Jones, B. E.,
R. Ryu,
Z. Yang,
M. D. Cave,
J. M. Pogoda,
M. Otaya, and
P. F. Barnes.
1997.
Chest radiographic findings in patients with tuberculosis with recent or remote infection.
Am. J. Respir. Crit. Care Med.
156:
1270-1273
.
