Standards for Diagnosis

Not all patients with respiratory symptoms receive an adequate evaluation for tuberculosis. These failures result in missed opportunities for earlier detection of tuberculosis and lead to increased disease severity for the patients and a greater likelihood of transmission of M. tuberculosis to family members and others in the community.

STANDARD 1.

All persons with otherwise unexplained productive cough lasting two–three
weeks or more should be evaluated for tuberculosis.

Rationale and Evidence Summary

The most common symptom of pulmonary tuberculosis is persistent, productive cough,
often accompanied by systemic symptoms, such as fever, night sweats, and weight loss.

In addition, findings such as lymphadenopathy, consistent with concurrent extrapulmonary
tuberculosis, may be noted, especially in patients with HIV infection.
Although most patients with pulmonary tuberculosis have cough, the symptom is not
specific to tuberculosis; it can occur in a wide range of respiratory conditions, including
acute respiratory tract infections, asthma, and chronic obstructive pulmonary disease.

Although the presence of cough for 2–3 weeks is nonspecific, traditionally, having cough
of this duration has served as the criterion for defi ning suspected tuberculosis and is used
in most national and international guidelines, particularly in areas of moderate – to high prevalence
of tuberculosis.22–25

In a recent survey conducted in primary healthcare services of nine low- and middleincome
countries, respiratory complaints, including cough, constituted on average 18.4%
of symptoms that prompted a visit to a health center for persons older than 5 years of
age. Of this group, 5% of patients overall were categorized as possibly having tuberculosis
because of the presence of an unexplained cough for more than 2–3 weeks.26 Other studies have shown that 4–10% of adults attending outpatient health facilities in developing
countries may have a persistent cough of more than 2–3 weeks in duration.27 This percentage
varies somewhat, depending on whether there is active questioning concerning
the presence of cough. Respiratory conditions, therefore, constitute a substantial proportion
of the burden of diseases in patients presenting to primary healthcare services.26,27
Data from India, Algeria, and Chile generally show that the percentage of patients with
positive sputum smears increases with increasing duration of cough from 1–2 weeks,
increasing to 3–4, and >4 weeks.28 However, in these studies even patients with shorter
duration of cough had an appreciable prevalence of tuberculosis. A more recent assessment
from India demonstrated that by using a threshold of > 2 weeks to prompt collection
of sputum specimens, the number of patients with suspected tuberculosis increased
by 61%, but more importantly, the number of tuberculosis cases identifi ed increased by
46%, compared with a threshold of >3 weeks.29 The results also suggested that actively
inquiring as to the presence of cough in all adult clinic attendees may increase the yield
of cases; 15% of patients who, without prompting, volunteered that they had cough,
had positive smears, but in addition, 7% of patients who did not volunteer that they had
cough, but on questioning admitted to having cough >2 weeks, had positive smears.29

Choosing a threshold of 2–3 weeks is an obvious compromise, and it should be recognized
that, while using this threshold reduces the clinic and laboratory workload, some
cases would be missed. In patients presenting with chronic cough, the proportion of
cases attributable to tuberculosis will depend on the prevalence of tuberculosis in the
community.27 In countries with a low prevalence of tuberculosis, it is likely that chronic
cough will be due to conditions other than tuberculosis. Conversely, in high-prevalence
countries, tuberculosis will be one of the leading diagnoses to consider, together with
other conditions, such as asthma, bronchitis, and bronchiectasis, that are common in
many areas.

Overall, by focusing on adults and children presenting with chronic cough, the chances
of identifying patients with pulmonary tuberculosis are maximized. Unfortunately, several
studies suggest that not all patients with respiratory symptoms receive an adequate evaluation
for tuberculosis.12,15,17–20,30 These failures result in missed opportunities for earlier
detection of tuberculosis and lead to increased disease severity for the patients and a
greater likelihood of transmission of M. tuberculosis to family members and others in the
community.