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Biomedical subjects

C Greenaway

Publications and source records attributed to C Greenaway.

8 recordsLinked to original sources
PubMed2006

False-positive tuberculin skin tests: what is the absolute effect of BCG and non-tuberculous mycobacteria?

BACKGROUND: Despite certain drawbacks, the tuberculin skin test (TST) remains in widespread use. Important advantages of the TST are its low cost, simplicity and interpretation based on extensive published literature. However, TST specificity is reduced by bacille Calmette-Guérin (BCG) vaccination and exposure to non-tuberculous mycobacteria (NTM). METHODS: To estimate TST specificity, we reviewed the published literature since 1966 regarding the effect of BCG vaccination and NTM infection on TST. Studies selected included healthy subjects with documented BCG vaccination status, including age at vaccination. Studies of NTM effect had used standardised NTM antigens in healthy subjects. RESULTS: In 24 studies involving 240,203 subjects BCG-vaccinated as infants, 20,406 (8.5%) had a TST of 10+ mm attributable to BCG, but only 56/5639 (1%) were TST-positive if tested > or =10 years after BCG. In 12 studies of 12,728 subjects vaccinated after their first birthday, 5314 (41.8%) had a false-positive TST of 10+ mm, and 191/898 (21.2%) after 10 years. Type of tuberculin test did not modify these results. In 18 studies involving 1,169,105 subjects, the absolute prevalence of false-positive TST from NTM cross-reactivity ranged from 0.1% to 2.3% in different regions. CONCLUSIONS: The effect on TST of BCG received in infancy is minimal, especially > or =10 years after vaccination. BCG received after infancy produces more frequent, more persistent and larger TST reactions. NTM is not a clinically important cause of false-positive TST, except in populations with a high prevalence of NTM sensitisation and a very low prevalence of TB infection.

Adjuvants, Immunologic↗
PubMed2005

Humoral response to Mycobacterium tuberculosis antigens in patients with tuberculosis in the Gambia.

OBJECTIVE: To determine and compare the sensitivity and specificity of four common mycobacterial antigens with three RD-1 region antigens in the serological diagnosis of active pulmonary tuberculosis (PTB) in the Gambia. DESIGN: Serum from 300 Gambians (100 with active PTB, 100 of their household contacts, and 100 community controls) was tested using an ELISA method to detect antibodies to seven mycobacterial antigens (three encoded in the RD-1 region [ESAT-6, CFP-10 and Rv3871] and four common [38 kDa, GLU-S, 19 kDa and 14 kDa]). Individuals with active TB were recruited from one of the National Leprosy and TB Control Program clinics in the western region of the Gambia, and neighborhood controls were an age-matched individual living within five houses of the case. RESULTS: The sensitivity of the RD-1 antigens ranged from 34% to 67%, while specificity ranged from 51% to 71%. The sensitivity of the common antigens ranged from 24% to 75% and specificity from 26% to 75%. CONCLUSION: In countries with high rates of TB, such as the Gambia, the clinical utility of serological testing to diagnose active TB remains limited, even with newer antigens encoded in the RD-1 region of Mycobacterium tuberculosis.

Adolescent↗
PubMed2004

Emissions from a vehicle fitted to operate on either petrol or compressed natural gas.

The purpose of this work was to evaluate the physical and chemical properties of emission products from a six-cylinder sedan car under a variety of operating conditions, before and after it has been converted to compressed natural gas (CNG) fuel. The specific focus of the measurements was on emission levels and characteristics of ultra fine particles and the emission levels together with the emissions of gaseous pollutants for a range of operating conditions before and up to 3 months after the vehicle was converted are presented and discussed in the paper. The investigations showed that converting a petrol operating vehicle to CNG has the potential of reducing some of the emissions and thus risks, while it does not appear to have an impact on others. In particular there was no statistically significant change in the emission of particles for the vehicle operating on petrol, before the conversion, compared to the emissions for the vehicle operating on CNG, after the conversion. There was a significant lowering of emissions of total polycyclic aromatic hydrocarbons and formaldehyde when the vehicle was operated on CNG, and a reduction of global warming potential was also observed when the vehicle was run on CNG, but the later gain is only at high vehicle speeds/loads, and would thus have to be considered in view of traffic and transport models for the region (in these models vehicle speed is an important parameter).

Journal Article↗
PubMed2003

Yield of casual contact investigation by the hour.

OBJECTIVE: Among casual contacts of tuberculosis (TB) patients, to assess how duration of contact, prior mycobacterial exposure, and performance of one or two tuberculin skin tests (TST), affect the likelihood that a positive TST represents conversion. METHODS: Published estimates of mycobacterial prevalence and BCG coverage, and their effect on single or repeated TSTs, were used to calculate baseline prevalence of TST reactions in four populations commonly encountered in North American contact investigations. Using published estimates of hourly risk of TB infection, the probability that a positive TST represented conversion was calculated. RESULTS: Among casual contacts with 20 hours of exposure, the likelihood that a single positive TST performed after 8 weeks represented conversion was 77% in persons from populations with low prior mycobacterial exposure, but only 6-8% in foreign-born populations. If tuberculin testing was performed immediately and then again 8 weeks post-exposure, 14-38% of all positive tests would be due to boosting, related to prior exposure to mycobacteria or BCG. If one TST, performed 8 weeks after exposure, was positive in casual contacts from populations with high prevalence of prior mycobacterial exposures, the likelihood of true conversion was less than 40%, even after 200 hours of exposure. CONCLUSIONS: A single TST performed 8 weeks after the end of exposure among casual contacts will detect all true conversions, and minimize misdiagnosis due to boosting. The decision to perform TST on casual contacts should consider the likelihood of prior mycobacterial exposure in the population, as well as the duration of exposure.

Adult↗
PubMed1998

The evolving epidemiology of chlamydial and gonococcal infections in response to control programs in Winnipeg, Canada.

OBJECTIVES: The purpose of this study was to describe and compare the transmission dynamics of chlamydia and gonorrhea in Winnipeg, Manitoba, Canada, and to assess implications for control programs. METHODS: Chlamydia and gonorrhea surveillance case reports (1988 through 1995) and contact-tracing reports (1991 through 1995) were examined. RESULTS: High incidence rates of both chlamydia and gonorrhea clustered in geographic core areas characterized by low socioeconomic status. A decline in the number of reported cases of chlamydia (61%) and gonorrhea (64%) occurred between 1988 and 1995. For chlamydia, the decline was most prominent in non-core area cases, while for gonorrhea it was similar in core and non-core areas. CONCLUSIONS: Chlamydia and gonorrhea appear to be evolving through different epidemic phases, with chlamydia transmission, in response to a newly introduced control program, becoming more core dependent and gonorrhea transmission becoming more sporadic in the face of a sustained control effort. Focused control programs, based on an understanding of the transmission dynamics of chlamydia and gonorrhea, may make their elimination a feasible goal.

Adolescent↗
PubMed1994

Methicillin-resistant Staphylococcus aureus. Optimization of the agar screen plate method.

Swab inoculation of oxacillin agar screen plates was compared with drop inoculation for detection of methicillin-resistant Staphylococcus aureus. The poor sensitivity of the swab method (59%) was related to heteroresistance of the S. aureus isolates. We recommend the drop method (100% sensitivity) because interpretation of results was significantly easier, making it more reliable.

Methicillin Resistance↗
PubMedDate not supplied

A foodborne outbreak causing a cholinergic syndrome.

We report a foodborne outbreak causing a cholinergic syndrome in three members of a family. The clinical presentation was characterized by nausea, vomiting, abdominal pain, and weakness. Physical examination revealed evidence of peripheral motor weakness and decreased level of consciousness in all three patients. Bradycardia, hypotension, and seizures occurred in two patients. Although initial therapy included administration of antitoxin for possible botulism, subsequent investigation revealed evidence of accidental organophosphate (fensulfothion) poisoning. The ubiquitous use of organophosphates as agricultural and household insecticides has ensured their continuing importance as causes of foodborne poisoning in both developed and developing countries. Physicians must remain alert to the possibility of non-bacterial causes of foodborne outbreaks in order to initiate prompt and appropriate investigations and specific therapy.

Aged↗