Recurrence of tuberculosis in a low-incidence setting.

Recurrence of active tuberculosis following treatment of an initial disease episode can occur due to endogenous re-activation or exogenous re-infection. Cases of recurrent tuberculosis in the Australian state of New South Wales between 1994 and 2006 were identified by data linkage analysis with confirmatory review of case notes. Patients with more than one culture-positive disease episode during that time period who had completed treatment for the initial disease episode were included. Genotyping of Mycobacterium tuberculosis was used to determine whether recurrence was likely to be due to re-activation or re-infection. There were 5,723 tuberculosis notifications between 1994 and 2006, 3,731 of which were culture-positive. Fifteen (0.4%) patients had recurrent culture-positive disease over a mean 5.7 yrs of follow-up (crude annual incidence 71 per 100,000 population). Recurrent tuberculosis was attributable to re-activation (indistinguishable strains) in 11 (73%) cases and to re-infection (different strains) in four (27%). In a low-incidence setting of tuberculosis, a control programme incorporating directly observed therapy for active disease resulted in a very low rate of recurrent tuberculosis over a long period of follow-up. Re-infection is less likely than re-activation, but still contributes significantly to the number of cases with recurrent disease.

Bronchoscopic diagnosis of endoscopically visible lung malignancies: should cytological examinations be carried out routinely?

BACKGROUND: The aim of this study was to determine the diagnostic yield of flexible bronchoscopy in endoscopically visible malignancies and to evaluate whether cytological examination, including bronchial washings and brushings, increase the diagnostic yield compared with bronchial biopsy alone. METHODS: We reviewed a series of bronchoscopies over a period of 7.5 years in which an endoscopically visible tumour was identified and which had a definite cytological or histological diagnosis of pulmonary malignancy obtained by bronchoscopy or any other examination. RESULTS: The criteria were met by 174 bronchoscopies. In 155 bronchoscopies all specimens including bronchial washings, brushings and biopsies were obtained; the overall diagnostic yield was 88%. This compared with a diagnostic yield of 77% for biopsies only (P < 0.001). The individual diagnostic yields for biopsies, brushings and washings were 77, 50 and 38%, respectively. The overall diagnostic yield of cytology was 61%, providing a diagnosis in 95 patients. Of 11 repeat bronchoscopies after an initial non-diagnostic bronchoscopy, 9 were diagnostic. CONCLUSION: The tumour detection rate with flexible bronchoscopy in endoscopically visible lung malignancies is high. Cytology-based sampling techniques by means of bronchial washings and brushings significantly increase the overall diagnostic yield compared with forceps biopsy only. Repeat bronchoscopies after an initial non-diagnostic bronchoscopy have a relatively high diagnostic yield and should therefore be considered in all patients with endoscopically visible tumour.

Radiographic predictors of subsequent reactivation of tuberculosis.

SETTING: A cohort of migrants to Australia (n = 7265) selected to be at increased risk of tuberculosis (TB) were assessed at the Liverpool Chest Clinic, Sydney, between 1984 and 2003. OBJECTIVE: To assess the reproducibility and predictive value of various radiographic criteria for predicting the subsequent development of TB. METHODS: A nested case control study was conducted. Cases were those who had a confirmed diagnosis of TB during follow-up (n = 60). A random sample of 107 controls was selected. Initial chest X-rays were read independently and blinded to case vs. control status by two readers according to two classification systems. Agreement was quantified as weighted kappa (kappaw). Sensitivity and specificity for subsequent TB were estimated. RESULTS: There was moderate agreement between readers for both classification systems (kappaw 0.67 and 0.60, respectively). The presence of calcified nodular densities or fibrosis together with non-calcified nodular densities in mid and/or upper lung zones or the presence of a pulmonary infiltrate typical of TB had a sensitivity of 66% for subsequent pulmonary TB and a specificity of 82%. Minor abnormalities or findings consistent with past primary TB infection alone were not predictive of subsequent TB. CONCLUSIONS: Radiographic screening can be helpful in identifying individuals at increased risk of subsequent TB.

A tidally breathing model of ventilation, perfusion and volume in normal and diseased lungs.

BACKGROUND: To simulate the short-term dynamics of soluble gas exchange (e.g. CO2 rebreathing), model structure, ventilation-perfusion (VA/Q) and ventilation-volume (VA/VA) parameters must be selected correctly. Some diseases affect mainly the VA/Q distribution while others affect both VA/Q and VA/VA distributions. Results from the multiple inert gas elimination technique (MIGET) and multiple breath nitrogen washout (MBNW) can be used to select VA/Q and VA/VA parameters, but no method exists for combining VA/Q and VA/VA parameters in a multicompartment lung model. METHODS: We define a tidally breathing lung model containing shunt and up to eight alveolar compartments. Quantitative and qualitative understanding of the diseases is used to reduce the number of model compartments to achieve a unique solution. The reduced model is fitted simultaneously to inert gas retentions calculated from published VA/Q distributions and normalized MBNWs obtained from similar subjects. Normal lungs and representative cases of emphysema and embolism are studied. RESULTS: The normal, emphysematous and embolism models simplify to one, three and two alveolar compartments, respectively. CONCLUSIONS: The models reproduce their respective MIGET and MBNW patient results well, and predict disease-specific steady-state and dynamic soluble and insoluble gas responses.