2021 State and City TB Report

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Sputum Culture Conversion

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Sputum culture conversion means that a patient had a positive sputum culture before being treated for TB disease but after starting treatment their sputum culture became negative. Successful sputum culture conversion is usually defined as at least two consecutive negative cultures. This conversion from positive to negative is the best way to measure how well a patient is responding to treatment and when achieved within the first 60 days of treatment will help determine the next treatment phase. Examining sputum on a regular basis also helps physicians:

• Detect failure to respond to therapy or early warning signs of relapse of TB disease
• Monitor multidrug-resistant TB patients to ensure they continue to respond to therapy
• Determine length of treatment (the longer it takes to convert, the longer the length of treatment)
• Document that the patient no longer has TB at the end of therapy

It can take up to 2 years to have full sputum culture conversion information reported for each TB patient. As a result, the most recent information available on sputum culture conversion is from patients in the 50 states and 9 cities who were identified with TB in 2019.

For these patients, 11 states and cities met or exceeded the 2025 national target of 83.0% of culture positive TB cases with documented culture conversion within 60 days of starting treatment; 21 states and cities were short of the 2025 target but met or exceeded the national average (69.4%) (Figure 10).