Use of Statistical Process Control Methods for Early Detection of Healthcare Facility–Associated Nontuberculous Mycobacteria Outbreaks: A Single-Center Pilot Study

Abstract

Background Nontuberculous mycobacteria (NTM) are emerging pathogens increasingly implicated in healthcare facility-associated (HCFA) infections and outbreaks. We analyzed the performance of statistical process control (SPC) methods in detecting HCFA NTM outbreaks. Methods We retrospectively analyzed 3 NTM outbreaks that occurred from 2013-2016 at a tertiary care hospital. The outbreaks consisted of pulmonary Mycobacterium abscessus complex (MABC) acquisition, cardiac surgery-associated extrapulmonary MABC infection, and a bronchoscopy-associated pseudo-outbreak of Mycobacterium avium complex (MAC). We analyzed monthly case rates of unique patients who had positive respiratory cultures for MABC, non-respiratory cultures for MABC, and bronchoalveolar lavage cultures for MAC, respectively. For each outbreak, we used these rates to construct a pilot moving average (MA) SPC chart with a rolling baseline window. We also explored the performance of numerous alternative control charts, including exponentially weighted moving average, Shewhart, and cumulative sum charts. Results The pilot MA chart detected each outbreak within 2 months of outbreak onset, preceding actual outbreak detection by an average of 6 months. Over a combined 117 months of pre- and post-outbreak surveillance, no false positive SPC signals occurred (specificity = 100%). Prospective use of this chart for NTM surveillance could have prevented an estimated 108 cases of NTM. Six high-performing alternative charts detected all outbreaks during the month of onset with specificities ranging from 85.7% to 94.9%. Conclusions SPC methods have potential to substantially improve HCFA NTM surveillance, promoting early outbreak detection and prevention of NTM infections. Additional study is needed to determine the best application of SPC for prospective HCFA NTM surveillance in other settings.

Risk Factors for and Outcomes Following Early Acquisition ofMycobacterium abscessusComplex After Lung Transplantation

“…Despite these interventions and successful outbreak mitigation, our center has subsequently identified sporadic hospital-associated MABC infections, which have led to additional safeguards [ 38 , 39 ]. Therefore, careful clinical surveillance for MABC and other NTM is critical to identify infections and potential outbreaks, promoting timely interventions [ 40 ].…”