CDC TB Screening Risk Classifications

This excerpt from the 2005 TB guidelines explains the new recommendations regarding risk assessment and TB testing:

The three TB screening risk classifications are low risk, medium risk, and potential ongoing transmission. The classification of low risk should be applied to settings in which persons with TB disease are not expected to be encountered, and, therefore, exposure to M. tuberculosis is unlikely. This classification should also be applied to HCWs who will never be exposed to persons with TB disease or to clinical specimens that might contain M. tuberculosis.

The classification of medium risk should be applied to settings in which the risk assessment has determined that HCWs will or possibly will be exposed to people with TB disease or to clinical specimens that might contain M. tuberculosis.

The classification of potential ongoing transmission should be temporarily applied to any setting (or group of HCWs) if evidence suggestive of person-to-person (e.g., patient-to-patient, patient-to-HCW, HCW-to-patient, or HCW-to-HCW) transmission of M. tuberculosis has occurred in the setting during the preceding year. Evidence of person-to-person transmission of M. tuberculosis includes 1) clusters of TST or BAMT conversions; 2) HCWs with confirmed TB disease; 3) increased rates of TST or BAMT conversions; 4) unrecognized TB disease in patients or HCWs; or 5) recognition of an identical strain of M. tuberculosis in patients or HCWs with TB disease identified by DNA fingerprinting.

If uncertainty exists regarding whether to classify a setting as low risk or medium risk, the setting typically should be classified as medium risk.

TB Screening Procedures for Settings (or HCWs) Classified as Low Risk

• All HCWs should receive baseline TB screening upon hire, using a two-step TST or a single BAMT to test for infection with M. tuberculosis.

• After baseline testing for infection with M. tuberculosis, additional TB screening is not necessary unless an exposure to M. tuberculosis occurs.

• HCWs with a baseline positive or newly positive test result for M. tuberculosis infection (i.e., TST or BAMT) or documentation of treatment for LTBI or TB disease should receive one chest radiograph result to exclude TB disease (or an interpretable copy within a reasonable time frame, such as six months). Repeat radiographs are not needed unless symptoms or signs of TB disease develop or unless recommended by a clinician.

TB Screening Procedures for Settings (or HCWs) Classified as Medium Risk

• All HCWs should receive baseline TB screening upon hire, using a two-step TST or a single BAMT to test for infection with M. tuberculosis.

• After baseline testing for infection with M. tuberculosis, HCWs should receive TB screening annually (i.e., symptom screen for all HCWs and testing for infection with M. tuberculosis for HCWs with baseline negative test results).

• HCWs with a baseline positive or newly positive test result for M. tuberculosis infection or documentation of previous treatment for LTBI or TB disease should receive one chest radiograph result to exclude TB disease. Instead of participating in serial testing, HCWs should receive a symptom screen annually. This screen should be accomplished by educating the HCW about symptoms of TB disease and instructing the HCW to report any such symptoms immediately to the occupational health unit. Treatment for LTBI should be considered in accordance with CDC guidelines.

TB Screening Procedures for Settings (or HCWs) Classified as Potential Ongoing Transmission

• Testing for infection with M. tuberculosis might need to be performed every eight to 10 weeks until lapses in infection control have been corrected and no additional evidence of ongoing transmission is apparent.

• The classification of potential ongoing transmission should be used as a temporary classification only. It warrants immediate investigation and corrective steps. After a determination that ongoing transmission has ceased, the setting should be reclassified as medium risk. Maintaining the classification of medium risk for at least one year is recommended.

Inpatient Settings with More Than 200 Beds

• If fewer than six TB patients for the preceding year, classify as low risk. If greater than or equal to six TB patients for the preceeding year, classify as medium risk.

Inpatient Settings with Fewer Than 200 Beds

• If fewer than three TB patients for the proceeding year, classify as low risk. If greater than or equal to three TB patients for the preceeding year, classify as medium risk.

Outpatient, Outreach, and Home-Based Healthcare Settings

• If fewer than three TB patients for the preceding year, classify as low risk. If greater than or equal to three TB patients for the preceeding year, classify as medium risk.