Some pleural effusions labeled as idiopathic could be produced by the inhalation of silica

Objectives Exposure to silica nanoparticles has been associated with pleural effusions (PEs) in animal models and case series. We hypothesized that some PEs labelled as “idiopathic” could, in fact, be secondary to inhalation of silica. Methods A retrospective case control study was designed utilizing a prospectively maintained pleural database. Cases, represented by idiopathic PEs, were matched by age and gender to control patients who had been diagnosed with malignant, cardiac, or infectious PEs. A survey consisting of questions about occupational life and possibility of silica inhalation was conducted. In a subgroup of patients, pleural fluid concentrations of silica were quantified by plasma atomic emission spectrometry analysis. Also, the pleural biopsy of a silica-exposed case was subjected to an energy dispersive X-ray spectroscopy (EDX) to identify the mineral, the size of which was determined by electron microscopy. Results A total of 118 patients (59 cases and 59 controls) completed the survey. There were 25 (42%, 95% CI 31–55%) and 13 (22%, 95% CI 13–34%) silica-exposed workers in case and control groups, respectively. The exposure attributable fraction was 0.62 (95% CI 0.14–0.83). Four of eight exposed cases showed detectable levels of silica in the pleural fluid (mean 2.37 mg/L), as compared to none of 16 tested controls. Silica nanoparticles of 6–7 nm were identified in the pleural biopsy of an exposed case patient. Conclusions It is plausible that some idiopathic PEs could actually be caused by occupational silica inhalation.

New approaches to disease causation research based on the sufficient-component cause model

Up to date, the sufficient-component cause model seems to be a theoretical framework for disease causation in epidemiology, and its implications in epidemiological research methods is currently still limited. Recently, pitfalls in current epidemiological research methods were addressed based on the sufficient-component cause model; hence, new research approaches are needed as alternatives. Therefore, this paper aims to review and suggest new epidemiological methods used to assess disease causation. A new approach was discussed to identify potential mechanisms of disease occurrence which may be useful for risk prediction and disease prevention. In addition, a novel “exposed case-control” design was introduced to identify potential component causes. Furthermore, this paper suggested a new approach of conducting a systematic review/meta-analysis related to causation studies.

Human bovine tuberculosis – remains in the differential

Mycobacterium bovis is a pathogen of cattle. The unpasteurized milk of affected cattle is a source of infection in humans. Despite the screening of cattle and the pasteurization of milk, M bovis has not been eradicated. A high index of clinical suspicion is needed in symptomatic patients with a history of possible exposure. At risk groups include animal workers, farmers, meat packers, vets and zoo keepers. Humans are usually infected by the aerosol route. We present two cases of human bovine tuberculosis. One was a presumptive case and the second was a confirmed case. Both responded well to antituberculous therapy. In the confirmed case, there was evidence of transmission to the partner living in the same house. Rifampicin prophylaxis was given to the exposed case. The M. bovis from the confirmed case was isoniazid resistant, in addition to having the well known resistance to pyrazinamide. Isoniazid resistance has been described before in those who are immunocompromised. We describe it in an immunocompetent patient.