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The role of the interferon gamma release assay in assessing recent tuberculosis transmission in a hospital incident.

Bradshaw L, Davies E, Devine M, Flanagan P, Kelly P, O'Connor K, Drobniewski F, Nikolayevskyy V, Abubakar I - PLoS ONE (2011)

Bottom Line: We also described within-patient variability of IGRA results.Among patients and staff, increasing age of patients was the only factor associated with IGRA positivity.Greatest within-subject variability of IU/mL in serially-tested patients/staff was seen in those with a positive IGRA test and this did not correlate with increased exposure to the index case.

View Article: PubMed Central - PubMed

Affiliation: Tuberculosis Section, Respiratory Diseases Department, Health Protection Agency Centre for Infections, London, England. louise.bradshaw@hpa.org.uk

ABSTRACT
In 2007, an extensive contact screening investigation into onward transmission of tuberculosis was instigated at a hospital in Northern Ireland following diagnosis of pulmonary multi-drug resistant TB in a healthcare worker. Interferon gamma release assays (IGRAs) were used to test 333 patients and 98 staff. We investigated for evidence of onward transmission and recent infection based on analysis of clinical, demographic and IGRA data. We also described within-patient variability of IGRA results. Among patients and staff, increasing age of patients was the only factor associated with IGRA positivity. Greatest within-subject variability of IU/mL in serially-tested patients/staff was seen in those with a positive IGRA test and this did not correlate with increased exposure to the index case. IGRA positivity being largely explained by increasing age in patients and previous TB contact in staff lends weight to the conclusion that IGRA positivity reflected previous infection rather than recent transmission.

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Related in: MedlinePlus

Patient follow-up.
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pone-0020770-g001: Patient follow-up.

Mentions: Patients whose initial test was indeterminate but whose second test returned a negative result were regarded as not infected and no further action was taken (see Figure 1). Of patients who were indeterminate on two tests six to eight weeks apart, or negative on the first test and indeterminate on a second, those with a previous history of TB; those with a visible healed tissue on chest x-ray; and those with old calcified disease on chest x-ray were excluded from active further follow-up. The case notes and available radiology were reviewed for all patients with a positive IGRA blood test, and they were followed-up as though they had recent infection. They were kept under out-patient department review for over two years since last possible contact with the index case (the period over which they are at greatest risk of progression to active disease) ending August 2009, after which they were discharged with letters sent to their General Practitioners. Over this period, chest x-rays were taken at intervals of: 6–8 months; 16–18 months; and at two years. Provision was made for review on request if they developed symptoms of TB. No chemoprophylaxis was offered.


The role of the interferon gamma release assay in assessing recent tuberculosis transmission in a hospital incident.

Bradshaw L, Davies E, Devine M, Flanagan P, Kelly P, O'Connor K, Drobniewski F, Nikolayevskyy V, Abubakar I - PLoS ONE (2011)

Patient follow-up.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3113857&req=5

pone-0020770-g001: Patient follow-up.
Mentions: Patients whose initial test was indeterminate but whose second test returned a negative result were regarded as not infected and no further action was taken (see Figure 1). Of patients who were indeterminate on two tests six to eight weeks apart, or negative on the first test and indeterminate on a second, those with a previous history of TB; those with a visible healed tissue on chest x-ray; and those with old calcified disease on chest x-ray were excluded from active further follow-up. The case notes and available radiology were reviewed for all patients with a positive IGRA blood test, and they were followed-up as though they had recent infection. They were kept under out-patient department review for over two years since last possible contact with the index case (the period over which they are at greatest risk of progression to active disease) ending August 2009, after which they were discharged with letters sent to their General Practitioners. Over this period, chest x-rays were taken at intervals of: 6–8 months; 16–18 months; and at two years. Provision was made for review on request if they developed symptoms of TB. No chemoprophylaxis was offered.

Bottom Line: We also described within-patient variability of IGRA results.Among patients and staff, increasing age of patients was the only factor associated with IGRA positivity.Greatest within-subject variability of IU/mL in serially-tested patients/staff was seen in those with a positive IGRA test and this did not correlate with increased exposure to the index case.

View Article: PubMed Central - PubMed

Affiliation: Tuberculosis Section, Respiratory Diseases Department, Health Protection Agency Centre for Infections, London, England. louise.bradshaw@hpa.org.uk

ABSTRACT
In 2007, an extensive contact screening investigation into onward transmission of tuberculosis was instigated at a hospital in Northern Ireland following diagnosis of pulmonary multi-drug resistant TB in a healthcare worker. Interferon gamma release assays (IGRAs) were used to test 333 patients and 98 staff. We investigated for evidence of onward transmission and recent infection based on analysis of clinical, demographic and IGRA data. We also described within-patient variability of IGRA results. Among patients and staff, increasing age of patients was the only factor associated with IGRA positivity. Greatest within-subject variability of IU/mL in serially-tested patients/staff was seen in those with a positive IGRA test and this did not correlate with increased exposure to the index case. IGRA positivity being largely explained by increasing age in patients and previous TB contact in staff lends weight to the conclusion that IGRA positivity reflected previous infection rather than recent transmission.

Show MeSH
Related in: MedlinePlus