Radiological cavitation, sputum mycobacterial load and treatment response in pulmonary tuberculosis

SETTING

Royal Free Hospital, London.

OBJECTIVE

To investigate the relationship between sputum mycobacterial load, assessed by time to positivity (TTP) in liquid culture, radiological cavitation and change in sputum bacterial load in response to anti-tuberculosis treatment.

DESIGN

The study was conducted on 95 patients treated for sputum culture-positive pulmonary tuberculosis (TB), with pre-treatment TTP and baseline chest X-ray (CXR). Of these, 31 had chest computed tomography scans assessed for number and volume of cavities. The microbiological treatment response was measured in 56 patients with serial TTP, and related to baseline radiological cavitation.

RESULTS

Cavitation was present in 48% of patients, and was associated with a shorter TTP at baseline (P < 0.001). Patients with more cavities and greater total cavitary volume had a shorter TTP (P < 0.001 for both). No difference was demonstrated in the rate of change in TTP on treatment (P = 0.36) between patients with and without cavities.

CONCLUSION

This study confirms that cavitation is associated with higher baseline sputum mycobacterial load. The rate of decline in bacterial load in response to treatment is similar in patients with and without radiologically demonstrable cavities, suggesting that response to, and hence duration of, effective treatment may be predicted by the initial number of organisms present in the sputum.

How good are systemic symptoms and blood inflammatory markers at detecting individuals with tuberculosis?

SETTING

The diagnosis of tuberculosis (TB) may be rejected in the absence of symptoms such as fever, sweats or weight loss.

OBJECTIVES

To determine how frequently these features and blood test evidence of inflammation were absent in individuals with TB.

METHODS

Prospective cohort study of 175 unselected subjects diagnosed with TB at a UK TB service between 2003 and 2006.

RESULTS

Eight (5%) subjects identified by screening and 24 (14%) without culture confirmation were excluded. Of the remaining 143, fever, sweats or weight loss were absent in respectively 37%, 39% and 38%. All three symptoms were absent in 25%. In 88 subjects with pulmonary disease, all three symptoms were absent in 20% (10% of smear-positive cases). Overall, C-reactive protein was normal in 15%, erythrocyte sedimentation rate in 21% and lactate dehydrogenase in 55%. In a multivariable model, factors associated with absent symptoms included drug-resistant TB (adjusted odds ratio [aOR] 3.58, P = 0.004) and female sex (aOR 3.15, P = 0.004).

CONCLUSIONS

In our population, TB, including pulmonary disease, frequently presented without fever, sweats or weight loss and with normal blood inflammatory markers. This information is of as much relevance to policy makers seeking to improve active case detection as to clinicians and the general public.