A pseudo-outbreak of purified protein derivative skin-test conversions caused by inappropriate testing materials.

OBJECTIVE

To investigate a cluster of newly identified tuberculosis infections.

DESIGN

A field study was conducted including interviews; medical record reviews; checking of bills and invoices, pharmacy records, and drug manufacturer information; and clinical retesting.

SETTING

Community residential facilities providing comprehensive services to retarded adults.

PARTICIPANTS

Twenty residential facility staff (not previously known to be purified protein derivative [PPD] positive).

RESULTS

Staff had been tested with 250 TU of PPD, and 9 of 20 were tuberculin positive. Retesting with 5 TU yielded no reaction.

CONCLUSIONS

Reactions were attributable to testing with a product not recommended for routine PPD screening. Healthcare workers planting PPD Mantoux tests always should check the vials to ensure that the appropriate strength solution is being used.