There was a 20% decline in reported cases of tuberculosis (TB) in the United States in 2020 compared with previous years, which was not a result of underreporting but did raise concerns that TB was underdiagnosed, researchers said.
“This drop was dramatically different from the average yearly decrease of 2% to 3% observed over the past 10 years,” Kathryn Winglee, PhD, a statistician in the CDC’s Division of Tuberculosis Elimination, told Healio. “CDC explored whether this decrease could have been caused by underreporting due to strains on the public health system from the COVID-19 pandemic.”
Winglee and colleagues compared trends of prescriptions for TB medications with reported TB cases to determine if the number of patients who were likely treated for TB differed from the number of cases reported by public health departments.
Overall, the data showed large declines in 2020 “strongly correlating” with national TB surveillance case counts, which researchers said helped rule out underreporting as a cause. According to the study, NTSS case counts decreased every year except 2007 and 2014, with 2009 seeing the largest decrease before 2020. They said the 2020 decrease is larger than previously reported because the treatment start date is missing for 2.8% of cases counted in 2019 and 5.2% of cases counted in 2020.
Similarly, the researchers found that the isoniazid IQVIA projected patient counts generally decreased each year, with 2020 seeing the largest decrease (28.6%). However, the pyrazinamide IQVIA patient counts revealed 4 years during which more cases occurred than the previous year 2014, 2015, 2017 and 2019. Azithromycin IQVIA data also showed multiple years with more projected patients than the previous year but a large drop in 2020 of 25.9%.
Researchers then analyzed whether the large declines in 2020 were within the error of what was expected based on previous trends. Overall, they found that most of the data within the 95% prediction interval with the April to December 2020 NTSS monthly case counts and IQVIA isoniazid projected patient counts were all below the lower bound of the 95% prediction interval. In contrast, however, the IQVIA projected patient counts for pyrazinamide, were only lower than the 95% prediction interval in April.
“This analysis has helped to rule out underreporting of TB cases as a cause of the 2020 decline, since the trends in TB prescriptions are similar to the trends in reported TB cases,” Winglee said. “However, concerns remain about missed or delayed diagnoses of tuberculosis disease.”
Because of this, she said health care providers “should think TB,” especially for patients with risk factors and symptoms of tuberculosis disease.
“Timely diagnoses of TB disease save lives and prevent further spread in our communities,” she said.
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