Unexpected decline in tuberculosis cases coincident with economic recession -- United States, 2009

<p>Abstract</p> <p>Background</p> <p>Since 1953, through the cooperation of state and local health departments, the U.S. Centers for Disease Control and Prevention (CDC) has collected information on incident cases of tuberculosis (TB) disease in the United States. In 2009, TB case rates declined -11.4%, compared to an average annual -3.8% decline since 2000. The unexpectedly large decline raised concerns that TB cases may have gone unreported. To address the unexpected decline, we examined trends from multiple sources on TB treatment initiation, medication sales, and laboratory and genotyping data on culture-positive TB.</p> <p>Methods</p> <p>We analyzed 142,174 incident TB cases reported to the U. S. National Tuberculosis Surveillance System (NTSS) during January 1, 2000-December 31, 2009; TB control program data from 59 public health reporting areas; self-reported data from 50 CDC-funded public health laboratories; monthly electronic prescription claims for new TB therapy prescriptions; and complete genotyping results available for NTSS cases. Accounting for prior trends using regression and time-series analyses, we calculated the deviation between observed and expected TB cases in 2009 according to patient and clinical characteristics, and assessed at what point in time the deviation occurred.</p> <p>Results</p> <p>The overall deviation in TB cases in 2009 was -7.9%, with -994 fewer cases reported than expected (<it>P </it>< .001). We ruled out evidence of surveillance underreporting since declines were seen in states that used new software for case reporting in 2009 as well as states that did not, and we found no cases unreported to CDC in our examination of over 5400 individual line-listed reports in 11 areas. TB cases decreased substantially among both foreign-born and U.S.-born persons. The unexpected decline began in late 2008 or early 2009, and may have begun to reverse in late 2009. The decline was greater in terms of case counts among foreign-born than U.S.-born persons; among the foreign-born, the declines were greatest in terms of percentage deviation from expected among persons who had been in the United States less than 2 years. Among U.S.-born persons, the declines in percentage deviation from expected were greatest among homeless persons and substance users. Independent information systems (NTSS, TB prescription claims, and public health laboratories) reported similar patterns of declines. Genotyping data did not suggest sudden decreases in recent transmission.</p> <p>Conclusions</p> <p>Our assessments show that the decline in reported TB was not an artifact of changes in surveillance methods; rather, similar declines were found through multiple data sources. While the steady decline of TB cases before 2009 suggests ongoing improvement in TB control, we were not able to identify any substantial change in TB control activities or TB transmission that would account for the abrupt decline in 2009. It is possible that other multiple causes coincident with economic recession in the United States, including decreased immigration and delayed access to medical care, could be related to TB declines. Our findings underscore important needs in addressing health disparities as we move towards TB elimination in the United States.</p

Tuberculosis Infection in the United States: Prevalence Estimates from the National Health and Nutrition Examination Survey, 2011-2012

<div><p>Background</p><p>Reexamining the prevalence of persons infected with tuberculosis (TB) is important to determine trends over time. In 2011–2012 a TB component was included in the National Health and Nutrition Examination Survey (NHANES) to estimate the reservoir of persons infected with TB.</p><p>Methods</p><p>Civilian, noninstitutionalized U.S. population survey participants aged 6 years and older were interviewed regarding their TB history and eligibility for the tuberculin skin test (TST) and interferon gamma release assay (IGRA) blood test. Once eligibility was confirmed, both tests were conducted. Prevalence and numbers of TST positive (10 mm or greater), IGRA positive, and both TST and IGRA positive were calculated by adjusting for the complex survey design after applying corrections for item nonresponse and digit preference in TST induration measurements. To examine TST positivity over time, data from NHANES 1999–2000 were reanalyzed using the same statistical methods. The TST was performed using Tubersol, a commercially available purified protein derivative (PPD), rather than PPD-S, which was the antigen used in NHANES 1999–2000. Prior patient history of TB vaccination was not collected in this study nor were patients examined for the presence of a Bacillus of Calmette and Guerin (BCG) vaccine scar.</p><p>Results</p><p>For NHANES 2011–2012, TST and IGRA results were available for 6,128 (78.4%) and 7,107 (90.9%) eligible participants, respectively. There was no significant difference between the percentage of the U.S. population that was TST positive in 2011–2012 (4.7% [95% CI 3.4–6.3]; 13,276,000 persons) compared with 1999–2000 (4.3%; 3.5–5.3). In 2011–2012 the percentage that was IGRA positive was 5.0% (4.2–5.8) and double TST and IGRA positivity was 2.1% (1.5–2.8). The point estimate of IGRA positivity prevalence in foreign-born persons (15.9%; 13.5–18.7) was lower than for TST (20.5%; 16.1–25.8) in 2011–2012. The point estimate of IGRA positivity prevalence in U.S.-born persons (2.8%; 2.0–3.8) was higher than for TST (1.5%; 0.9–2.6).</p><p>Conclusions</p><p>No statistically significant decline in the overall estimated prevalence of TST positivity was detected from 1999–2000 to 2011–2012. The prevalence of TB infection, whether measured by TST or IGRA, remains lower among persons born in the United States compared with foreign-born persons.</p></div

Tuberculin Skin Test Positive Prevalence in the Civilian, Noninstitutionalized U.S. Population, Ages 6+, 2011–2012 and 1999–2000.

<p>^a Calculated for characteristics for which a population denominator was available</p><p>^b Estimates for Hispanic and Asian subgroups cannot be calculated for 1999–2000 due to NHANES sampling methodology</p><p>^cDefined using the ratio of family income to poverty (calculated by dividing family income by the U.S. Department of Health and Human Services poverty guidelines specific to the survey year); < 1 was considered below poverty</p><p>^d Normal, prediabetes and diabetes were defined using the National Institutes of Health’s glycohemoglobin (A1C) cutoff values <a href="http://diabetes.niddk.nih.gov/dm/pubs/diagnosis/" target="_blank">http://diabetes.niddk.nih.gov/dm/pubs/diagnosis/</a></p><p>^e BMI categories for children and adolescents aged 2 to 19 years were based on the Centers for Disease Control and Prevention's sex-specific 2000 BMI-for-age growth charts for the United States <a href="http://www.cdc.gov/growthcharts/clinical_charts.htm" target="_blank">http://www.cdc.gov/growthcharts/clinical_charts.htm</a>. BMI for adults aged 20 years and older were based on Centers for Disease Control and Prevention’s standard weight status categories <a href="http://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html" target="_blank">http://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html</a></p><p>^§ Estimates and 95% CIs may be unreliable because the RSE > 30%</p><p>Note: There were no study participants with both TST positive and HIV positive results</p><p>Tuberculin Skin Test Positive Prevalence in the Civilian, Noninstitutionalized U.S. Population, Ages 6+, 2011–2012 and 1999–2000.</p

Tuberculin Skin Test and Interferon Gamma Release Assay Positive Prevalence in the Civilian, Noninstitutionalized U.S. Population, Ages 6+, 2011–2012.

<p>* Estimates and 95% CIs may be unreliable because the number of sample positives is < 10</p><p>^§ Estimates and 95% CIs may be unreliable because the RSE > 30%</p><p>Tuberculin Skin Test and Interferon Gamma Release Assay Positive Prevalence in the Civilian, Noninstitutionalized U.S. Population, Ages 6+, 2011–2012.</p

Flow chart illustrating participation in the 2011–2012 National Health and Nutrition Examination Survey, including total survey participants and number and percentage of survey participants who had tuberculin skin and interferon gamma release assay tests and results.

<p>Flow chart illustrating participation in the 2011–2012 National Health and Nutrition Examination Survey, including total survey participants and number and percentage of survey participants who had tuberculin skin and interferon gamma release assay tests and results.</p

Tuberculin Skin Test Positive Prevalence in the Civilian, Noninstitutionalized U.S.-born Population, Ages 6+, United States, 2011–2012 and 1999–2000.

<p>^a Estimates for Hispanic and Asian subgroups cannot be calculated for 1999–2000 due to NHANES sampling methodology</p><p>*Estimates and 95% CIs may be unreliable because the number of sample positives is < 10</p><p>^§ Estimates and 95% CIs may be unreliable because the RSE > 30%</p><p>Tuberculin Skin Test Positive Prevalence in the Civilian, Noninstitutionalized U.S.-born Population, Ages 6+, United States, 2011–2012 and 1999–2000.</p

Tuberculin Skin Test Positive Prevalence in the Civilian, Noninstitutionalized Foreign-born Population, Ages 6+, United States, 2011–2012 and 1999–2000.

<p>^a Estimates for Hispanic and Asian subgroups cannot be calculated for 1999–2000 due to NHANES sampling methodology</p><p>* Estimates and 95% CIs may be unreliable because the number of sample positives is < 10</p><p>^§ Estimates and 95% CIs may be unreliable because the RSE > 30%</p><p>Tuberculin Skin Test Positive Prevalence in the Civilian, Noninstitutionalized Foreign-born Population, Ages 6+, United States, 2011–2012 and 1999–2000.</p

Interferon Gamma Release Assay Positive Prevalence in the Civilian, Noninstitutionalized U.S. Population, Ages 6+, 2011–2012.

<p>^a There were no foreign-born study participants with both IGRA positive and HIV positive results</p><p>* Estimates and 95% CIs may be unreliable because the number of sample positives is < 10</p><p>^§ Estimates and 95% CIs may be unreliable because the RSE > 30%</p><p>Interferon Gamma Release Assay Positive Prevalence in the Civilian, Noninstitutionalized U.S. Population, Ages 6+, 2011–2012.</p

Agreement between the Tuberculin Skin Test and Interferon Gamma Release Assay Test Results for Tuberculosis Infection in the Civilian, Noninstitutionalized U.S. Population, Ages 6+, 2011–2012.

<p>Agreement between the Tuberculin Skin Test and Interferon Gamma Release Assay Test Results for Tuberculosis Infection in the Civilian, Noninstitutionalized U.S. Population, Ages 6+, 2011–2012.</p