1236 infection control & hospital epidemiology october 2017, vol. 38, no. 10


methods Healthcare Setting


Memorial Sloan Kettering Cancer Center (MSKCC) is a 473-bed cancer hospital inNew York City. Screening for latent TB infection (LTBI) with TST or interferon gamma release assay (IGRA) is performed annually for approximately 8,300 healthcare workers, with an overall conversion rate of <0.1% between 2005 and 2015. IGRAs are performed on HCWs with a positive pure protein derivative (PPD) or history of Bacillus Calmette-Guérin (BCG) vaccine. For HCWs with LTBI who decline treatment, active surveillance with a self- completed symptom screening questionnaire is performed annually. On average, 93 new cases of LTBI are diagnosed at MSKCC every year among newly hired employees. Among 111 new LTBI diagnoses in 2014, 86 (77%) occurred in foreign- born workers. Between 2004 and 2014, after counseling, 38.4% of these employees initiated therapy, with an overall completion rate of 76.5%.18


Investigation Description of index case and exposure setting. A 54-year-


old, foreign-born, HIV-negative nurse was diagnosed with cavitary pulmonary TB in January 2015 after experiencing nonresolving cough for 5 weeks. She was known to be PPD positive (30mm) formore than 20 years, and her baseline chest radiograph showed right-sided apical changes. Treatment for LTBI had been offered butwas declined on numerous occasions. The most proximate screening for symptoms of active TB was performed 5months prior to the onset of the cough. Chest x-ray at time of diagnosis showed a large, right-sided, cavitary lung lesion. Sputum examination was strongly positive for acid-fast bacilli by smear (3+), and culture from sputum grew isoniazid (INH)-resistantMTB after 14 days of incubation. The index caseHCW was assigned to cover a single inpatient


unit as part of her daily assignments. She used isolation pre- cautions for every patient following routine care standards. This unit is a 42-bed inpatient ward with 10 private rooms, including a single airborne infection isolation room; the remaining 16 rooms house 32 beds.The air-handling system on the unit allows 8 air changes per hour and incorporates a high-efficiency parti- culate air filtration system (99.97%retention). Patients admitted to the unit are surgical and medical cases, predominantly with head- and neck-related cancer diagnoses.Only patients who had direct contact with the index caseHCWwere considered at risk. Contact tracing. A multidisciplinary response team was assembled including representatives from infection prevention, employee health, nursing, clinical laboratories, health informatics, and administration. The contagious period was calculated based on the onset of cough until the last contact on the unit, as previously described.19 Nursing informatics created a logic-based query to identify


all patients for whom any documents had been authored by the index case HCW within the 3-month contact-tracing period


table 1. Interactions Based on Tracing of Documents Authored by the Index Case From Electronic Medical Records and Estimate Exposure Time for Each Event


Assessment Education Event note Medication Orders Other


Vital signs, intake and output Total interactions


No. of events Estimated time, min 227


176 37


1,712


3,131 5,947


120 15 60 15


250 No patient contact 414


10 10


for those included in the first tier was further refined by the susceptibility of the exposed patient (ie, underlying cancer type, positive HIV status, or transplant recipient). For patients with solid tumors, 2 interactions performed by the index HCWwith an estimated cumulative exposure time of ≥2 hours were considered significant. For those with underlying hema- tologic malignancy, stem-cell transplant recipients, or HIV- positive persons, any direct care was considered substantial exposure and was included in the first tier.20 For HCWs, first-tier exposure lists were created using the


from the electronic medical record system (EMR). Any inter- action that would require a face-to-face encounter with a patient was built into the query. These encounters covered all aspects of nursing care: nursing admission and daily assess- ments, patient education, recording event notes, obtaining vital signs, and medication administration. Based on these encounters, patients that received direct care from the index caseHCWwere initially identified. Next, time spent providing direct patient care was derived to estimate exposure times and cumulative risk (in hours) (Table 1). A concentric-circle approach was used; significant exposure


nursing schedule and the EMR to identify coworkers with overlapping shifts. Any HCW sharing any part of a work shift, defined by ≥8 hours of shared time on the same unit with the index caseHCWduring the contagious period, was considered to have had significant exposure.


results Patients


During the high-risk period, 270 patients were admitted to the unit (Figure 1). In total, 137 patients (50.7%) received direct care from the index case HCW, with a total of 5,947 recorded interactions. Of 137 patients, 63 patients (45%) met criteria for testing based on cumulative exposure and patient suscept- ibility as outlined above. The underlying cancer diagnoses for the 63 patients are shown in Table 2. These 63 patients had a median age of 63 years (range, 18–91 years), and 44 (69.8%) were male. In addition, 4 patients were considered high risk (1 HIV-positive patient and 3 patients with hematologic


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