Tuberculosis Contact Investigation: Eight Years of Experience with the QuantiFERON-TB®Gold In-Tube in Lower Saxony, Germany

Abstract

Since the beginning of the 21st century, beside tuberculin skin tests (TST) and chest X-rays, interferon-gamma release assays (IGRA) have become available for diagnosing latent tuberculosis infection. In 2006, the Governmental Institute of Public Health of Lower Saxony (NLGA) established the IGRA in its laboratory, using the QuantiFERON-TB®Gold In-Tube (QFT). A cohort of 19 309 contact persons who were investigated during contact tracing by local public health departments (LPHD) was analyzed. Within 3 years, 75% of LPHDs in Lower Saxony established the QFT for tuberculosis contact tracing. Between 2007 and 2014 the percentage of contact persons≥15 years of age with initial TST declined from 65.1 to 1.7%. For contact persons<15 years of age, this proportion declined from 81.7% (2007) to 10.1% (2014). The proportion of contact persons who reported a country of birth outside Germany rose from 21.3 to 28.8% between 2008 and 2013. Cases from South Eastern European countries were increasingly reported, seldom from states of the former Soviet Union. 14.1% of the investigated contact persons had a positive QFT. 449 persons with a negative result underwent a second test within 4 months; 4% of these tested positive. Within a period of 8 years, the TST was replaced by the QFT in Lower Saxony, not least because of the modified recommendations for environmental contact tracing in tuberculosis of the German Central Committee against Tuberculosis (DZK). Higher specificity of the QFT and thus fewer X-rays, omission of the second visit for interpreting the TST, and the inappropriate package size of the TST for smaller LPHDs are further arguments in favor for the QFT. But unspecific use of the QFT must be avoided; otherwise, the value of the QFT result declines. The increasing number of contact persons with migration background and the changing countries of origin are a challenge for all who are involved in tuberculosis contact tracing.