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When is referral of Heaf test positive schoolchildren worth while? Prospective study

BMJ 1996; 313 doi: http://dx.doi.org/10.1136/bmj.313.7059.726 (Published 21 September 1996) Cite this as: BMJ 1996;313:726
  1. Helen Booth, senior registrara,
  2. Christine Pollitt, paediatric registrar Christina Jessen, senior registrar in community paediatrics Andrew Cant, consultant in paediatric infectious diseasesb,
  3. E Christina Jessen, consultant respiratory physiciana,
  4. David J Hendrick, consultant respiratory physiciana,
  5. Andrew J Cant
  1. a Department of Respiratory Medicine, Newcastle General Hospital, Newcastle upon Tyne NE4 6BE,
  2. b Department of Paediatric Infectious Diseases
  1. Correspondence to: Dr Cant.
  • Accepted 17 June 1996

Recent guidelines for controlling and preventing tuberculosis recommend that no further action is required for children with a grade 2 reaction to Heaf testing in the school pre-BCG screening programme.1 Fifty seven per cent of district health authorities, however, still recommend referral for such children.2 Furthermore, no guidance is given regarding contact tracing of children who are confirmed to be tuberculin positive but who have no signs or symptoms of clinical disease. We prospectively studied the results of screening children referred to our childhood tuberculosis clinic after a positive school Heaf test from January 1991 to August 1994 and tracing the contacts of these children.

Methods and results

Newcastle Health Authority currently recommends referral of children with a positive Heaf test result of grade 2 or above to our childhood tuberculosis clinic. Tuberculin sensitivity is confirmed with a Mantoux test: 0.1 ml of 1:1000 purified protein derivative, read after 72 hours. Palpable induration of greater than 5 x 5 mm in children without a history of BCG vaccination and 10 x 10 mm in those with such a history is considered positive. Children with active tuberculosis based on clinical and radiological examinations are notified and started on a regimen of antituberculous drugs. Children with tuberculin sensitivity but no evidence of clinical disease are recorded as “Mantoux positive only” and offered prophylaxis with isoniazid.

Contact tracing follows locally established guidelines. All close family contacts have a chest x ray picture taken. All adults from the Indian subcontinent under 40 years old and children have a tuberculin sensitivity test in addition.

Details of all cases of tuberculosis and children who were Mantoux positive only are entered on to a database. Data on children referred from the school BCG programme and the results of contact tracing during the study period were extracted from this source.

Seventy eight schoolchildren (median age 12, range 5-14 years; 41 boys) were referred with positive Heaf test results and confirmed to be tuberculin positive (table 1). Six (four girls, two of whom were from the Indian subcontinent) had abnormal results in chest radiographs and were notified as having sputum smear negative pulmonary tuberculosis. Five of them (one from the Indian subcontinent) had been initially referred with Heaf test grade 2 positivity.

Table 1

Results (No (%)) of screening and contact tracing schoolchildren with positive responses to Heaf and Mantoux tests

View this table:

Two hundred and sixty nine out of 479 (56%) named contacts were screened. Two contacts of children with active tuberculosis had pulmonary tuberculosis: one was a younger white sibling, the other was an Indian mother with a cavitating apical lung lesion. Three contacts of children who were Mantoux positive only, all from the Indian subcontinent, were notified as having active tuberculosis: two were siblings of one index case, the other was a father with nodal tuberculosis. In addition, 18 further contacts of children who were Mantoux positive only were themselves found to be Mantoux positive. Thirteen of them were from the Indian subcontinent.

Comment

Our results suggest that all children with positive Heaf test results, including those with grade 2 results, should be referred for further assessment. In our clinic 62% of children with a grade 2 response on the school Heaf test and and 26% of those with a grade 3 response were Mantoux negative and considered to have given false positive Heaf test results. Tuberculin status should therefore be confirmed before further investigations are undertaken. This may partly explain why our rate (11%) of tuberculosis in those with grade 2 Heaf test results is higher than that reported in other series.3 4

A small percentage (2.9%) of contacts of children with grade 3 and 4 Heaf test responses but who were Mantoux positive only had active tuberculosis. This is a higher yield than that reported after contact tracing adult cases of pulmonary smear negative tuberculosis.5 Contact tracing a tuberculin positive child might be expected to be more likely to identify a source case, as being young they will have had fewer contacts and infection will have occurred more recently. Our results emphasise the need for thorough household investigation of children with Heaf test responses of grade >/=3. Contact tracing children referred with grade 2 Heaf test results, however, does not seem to be as worth while, though it identifies siblings who can then be offered chemoprophylaxis. Restricting contact tracing of Mantoux positive only children to those from the Indian subcontinent would have identified all cases of tuberculosis and 72% of tuberculin positive only contacts.

Footnotes

  • Funding None

  • Conflict of interest None.

References

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