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No. 2, 2011


The Evolution of Cohort Review in an Urban Setting – Experiences from Chicago, Illinois

The cohort review is a systematic review of TB patients and their contacts.  A “cohort” is a group of TB patients identified over a specific period of time, usually 3 months. Their cases are reviewed approximately 6-9 months after they are reported; thus, many of the patients have completed treatment or are nearing the end of treatment at the time when the cohort review is conducted.1 As part of the 2010-2015 cooperative agreements (CoAgs), TB programs are required to conduct at least one cohort review per year as part of program evaluation activities.2 CDC outlines three models for conducting a cohort review to account for program requirements and resources.2 Additionally, the CoAgs outline the frequency for cohort reviews depending on the program’s total number of TB cases per year.2 Chicago has been among the top 5 for cities reporting TB cases, with a record low incidence in 2010 of 161 cases. Chicago implemented the cohort review process in 2005.  This article illustrates the evolution of cohort review at the Chicago Department of Public Health (CDPH) TB program, from the method originally adopted in March 2005 to the method in operation as of March 2011.

In March 2005, members of the CDPH TB program received training on the cohort review process by the Charles B. Felton National Tuberculosis Center at Harlem Hospital and the New York City Department of Health and Mental Hygiene Bureau of Tuberculosis Control.  Chicago conducted its first cohort review in June 2005, 3 months following the initial training. Following the New York City cohort review model, TB cases were presented by the staff member who had most contact with the case, usually the case manager, contact investigator, or DOT outreach worker. The following data regarding TB cases, case management, and contact investigations were presented about each patient:

  • Patient’s clinical status
  • Patient’s treatment outcome
  • Adequacy of the medication regimen
  • Treatment adherence or completion
  • Results of contact investigation
  • Percentage of contacts who did, or are likely to, complete treatment

Each case was reviewed by the TB Medical Director, the TB Supervising Physician, and the Field Manager. All cases were presented sequentially, and data were entered into a spreadsheet by the epidemiologist, who would conduct real-time analyses and present results at the end of the day to the entire TB staff. After four quarters of conducting cohort review, Chicago evaluated its process. The most frequent feedback comments from staff were the following:

  • Most preparatory work was being done a few days prior to cohort review
  • Mandatory full-day meetings were long, tiring, and not applicable to all staff
  • Use of a standardized, repetitive script resulted in missed or limited learning opportunities

In response to this feedback, the CDPH modified the cohort review format in early 2007. With the new format, each clinic site had a designated time slot to present its cases before the TB Panel.  All other aspects of the initial cohort review process were maintained.  Because not all staff were present for the whole day, results were provided to staff later via e-mail and/or fax.

Cohort review continued with this format until 2010, when Chicago again evaluated its process. Comments from staff at this time were the following:

  • Cohort review resembled monthly case conferences
  • Limited utility for staff
  • Delayed results made cohort review incomplete

Based on this feedback, the CDPH again planned to restructure its cohort review process.  The objectives of this restructuring were to:

  • Utilize National TB Indicators as program evaluation outcome measures
  • Decrease the redundancy with case conferences
  • Make the meeting more meaningful and useful for staff
  • Identify areas for program improvement
  • Utilize data that TB staff were inputting into the surveillance system for Illinois
  • Use the Illinois-National Electronic Disease Surveillance System (I-NEDSS)

In order to achieve these goals, the cohort review process was dramatically changed, and a new process for data flow was developed (Figure 1).

Figure 1: Data Flow for Chicago Cohort Review in 2010
Figure 1: Data Flow for Chicago Cohort Review in 2010, see text version for full description

Text version

An initial cohort review list is generated using data from I-NEDSS and is sent to field staff who review and update missing or incomplete information. Data are then sent to CDC by the Illinois Department of Health (IDPH) via TIMS. CDC runs the NTIP analysis and sends a line list of cases not meeting the NTIP objective back to Chicago.  CDPH reviews the line list, cleans the data, and inserts missing information.  The cleaned data would again be sent to CDC, which would run an analysis and generate a new line list.  CDPH would again review the results and would generate a final line list of cases not meeting each NTIP objective. Cohort review would focus only on cases not meeting the NTIP objectives, allowing TB staff to identify gaps in patient care, contact investigations, and data management.

Patient X, see alt text below

Text version

In 2011, Chicago realized it needed a locally sustainable method for cohort review data analysis that did not rely on a CDC epidemiologist. Additionally, the new CDC guidelines for cohort review suggest TB programs should review every case in the cohort.  In response to these two concerns, CDPH modified its cohort review process, while retaining several aspects from the pilot project. CDPH continues to use NTIP indicators; however, analysis is conducted by CDPH using I-NEDSS data. Each patient’s case and his or her contacts are reviewed, but staff only focus on NTIP indicators where the objective was not met. Each case in the cohort will have its own slide (Figure 2). NTIP indicators not meeting the objective are color-coded in red; those in green have met the objective. Only red-colored variables are discussed during cohort review.  Because data are input by field staff on an ongoing basis, the cohort process is continuous throughout the year. 

Though there have been several revisions to Chicago’s cohort process, we believe the current model best addressed CDPH TB program needs. However, we would not have been successful if we had not listened to the staff feedback and been willing to re-evaluate our process frequently and make modifications. As we look to the future, we are hoping to expand the NTIP indicators that we currently review, and perhaps to include other variables that will assist with program evaluation.

—Submitted by Neha Shah, MD, MPH, DTBE Field Medical Officer, Chicago Dept of Public Health
Juan Elias, Supervising Communicable Disease Investigator, Chicago Dept of Public Health
Stephen E. Hughes, PhD, TB PEN Co-Chair, NY State Dept of Health


  1. CDC. Understanding the TB Cohort Review Process: Instruction Guide. Atlanta, GA: U.S. Dept. of Health and Human Services, CDC; 2006. Available at
  2. Moran J and Scavotto J. Dear Colleague letter and attached “CDC Division of Tuberculosis Elimination TB Cohort Review Guidance” [unpublished]. Atlanta, GA: CDC; August 9, 2010.

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