Presentation on theme: "TB Surveillance Using QuantiFERON® -TB Gold Is it measuring up?"— Presentation transcript:
1TB Surveillance Using QuantiFERON® -TB Gold Is it measuring up? Dr. David Marder, MD, MPHMedical Director of University Health ServiceUniversity of Illinois Medical Center Chicago
2Areas of Concern Estimated 10-15 million persons in U.S. infected with M. tuberculosis (60-90 M worldwide)Roughly 2-3 million deaths per year (worldwide)Drug-resistant cases reported in almost every stateWithout intervention, about 10% will developTB disease at some point in life
3Problems with TST… Poor inter-reader reliability 9 mm (negative) vs. 10mm (positive)?False-positives/specificityNTM infectionPrior BCGPoor positive-predictive value in low prevalence populations (like US)Cost/time of patient visitsUnread testsSensitivity?Reaction wanes over timeLack of gold standard
4• TB specific antigen, Nil &Mitogen tubes TB and the 21st Century; Introducing QuantiFERON® TB Gold ‘‘In-Tube’”In the field:• TB specific antigen, Nil &Mitogen tubes• Blood collected directly into tubesIn the lab:• ELISA for detection ofIFN gamma IFN-
5TB-Specific antigens (ESAT-6, CFP-10, TB7.7) Absent from BCGAbsent from most NTMProduced as synthetic peptidesOnly stimulate T-cells in infected people
7QuantiFERON®-TB GOLD Offers fundamental advantages over the TST: Single Patient Visit100% results, No need to follow up on negativesContacts, Homeless, Jail inmatesUnaffected by BCG and NTMHighly specific testReduces false positivesBetter detection of active TBIncreased sensitivity for active TB
8QuantiFERON®-TB GOLD Also: Objective and controlled test Reduces subjectivity in TB diagnosisSimple diagnostic cut-offStraight forward positive/negative interpretationEliminates 2 step testingNo ‘booster’ effectsFaster turn-around, results in hoursResults are electronic (computer generated reports)
9QuantiFERON®-TB GOLD Advantages (cont.) Reduces unnecessary CXR and prophylaxisReliable detection of post exposure LTBINot subject to reader bias
10QuantiFERON ® TB-Gold Implementation at UICMC First Brought up at TB Sub-Committee MeetingMultidisciplinary approach involving Pulmonary, Infection Control, Employee Health, Infection Disease, Laboratory and Environmental Health and Safety DepartmentReview of the Literature
11University Health Service at UICMC QuantiFERON ® TB-GOLD Pilot Program University Health Services (UHS) began exploring the new gamma-interferon assay in June 2005 as an alternative to the PPD skin test for screening Health Care Workers.With the University of Illinois Medical Center Chicago (UIMCC) laboratory, a pilot project began in August 2005.Full implementation of the Quantiferon surveillance program in January 2006.
12Moving forward w/ Pilot Study Support from Hospital AdministrationSupport from the Lab and Phlebotomy staff to assist w/ blood collection and turn around time on resultsRecruitment of employee’sPositive PPD groupNegative PPD group
13PILOT SUBJECTS79 health care workers were recruited for the pilot program from the following 3 groups:TST negativeTST positive/BCG negativeTST positive/BCG positive
14PILOT RESULTS25 out of 37 (68%) of previous TST positive were Quantiferon negative.In the BCG group alone, 11 (65%) were TST positive and Quantiferon negative.The decrease in positive TB tests will increase the number of employees who can affectively be screened for TB in the future with Quantiferon as opposed to the monitoring of symptoms by questionnaire as done in the past.
16We Did It! The Illinois Department of Public Health changes Tuberculosis screening law Control of Tuberculosis Code(77 Ill. Adm. Code 696)Illinois Register Citation: 32 Ill. Reg. 4010Date Published: March 14, 2008Effective Date: February 29, 2008The current rules on tuberculosis (TB) cover the screening, treatment, testing, management and reporting requirements for persons with active or suspected of TB, having TB disease or latent TB infection (LTBI). The rules previously required the use of the Mantoux tuberculin skin test (TST) as the only test approved for screening for LTBI. The amendment allows the use of a newly developed FDA-approved blood test for the detection of patients with active TB disease or LTBI. The amendment only adds the use of the new FDA approved blood test as an approved test for screening patients and does not remove the TST as an approved test for screening.
17UIMCC TB Control PlanIDPH - Tuberculosis Prevention and Exposure Control Plan, Section 7, Employee Surveillance: Previously only TST approved.IC Committee approved changes to the policy to include “…the current screening methodology which may include PPD, QuantiFERON-TB Gold, and any other approved /newly developed test…” November 2005.At this time QuantiFERON TB-Gold is the recommended form of testing for all Medical Center employees.
18Pre-Employment Screening At the time of employment, all UIMCC employees including those with a history for BCG vaccine shall receive a tuberculosis screening test, such as QuantiFERON® -TB Gold (QFT-G), or any other approved test.
19Pre-Employment Cont.All employees that have a positive tuberculosis screening test will be referred for a chest x-ray and medical evaluation. The employee shall be provided with documentation of his/her test results and instructed to consult with a personal physician regarding prophylactic therapy. A positive tuberculosis screening test will not affect employment status unless active TB disease is present
20Annual SurveillanceAll employees employed by UIC Medical Center and all those employed elsewhere that have patient contact shall have repeat tuberculosis screening test (annually or semi-annually in accordance with their unit or department schedule).
21An overview of UIMCC’s first year of QuantiFERON® testing
222006 RESULTS A total of 4643 QuantiFERON tests were completed in 2006. 4313 Negative (92.9%)140 Positive (3.0%)190 Indeterminate (4.1%)
232006 RESULTSA subset of the previous TST positive received QFT of the 505 were QFT negative (72%).
24Cost Evaluation Considerations Is QFT Cost Effective? Amount of collection timeSuppliesCost of testLaboratory support, time and costNurse time
25Other Possible Cost Evaluation Considerations Cost of medication and associated side effectsConvenience for employeesEmployee time away from work# of visits to employee healthFailure of ppd reads
26PROGRAM REVIEW ANALYSIS A cost benefit analysis was done in September.It showed considerable savings to the Medical Center, especially when the outreach lab did several thousand tests.This analysis did not take into account the lost time Health Care Workers incur when utilizing the TST.In 2006, there were 2,000 less visits to UHS since the program transitioned to the Quantiferon testing.
27PPD vs. QFT Cost Analysis Low end pricing Year Number of skin tests low end price Annual costYear $41 $205, Number of QFTs Year $25 $125,000.00Cost Savings $ 80,000.00/yr.* Statistics are extracted from the CDC Lambert Paper. All numbers are on the conservative side.
28PPD vs. QFT Cost Analysis National Average Year Number of skin tests Nat'l avg. price AnnualYear $100 $500,000.00Number of QFTs Year $25 $125,000.00Cost Savings $ 375,000.00/yr.
29CONVERSIONS & REVERSIONS Wobble effect – results may wobble around the 0.35 cutoff when tested serially. This can give results of positive one time and then negative next or visa versa.This variation occurs more with positive results than negative.
30QuantiFERON® TB-Gold “In Tube” Test Validation EVOLISQFTB-GTOTALPOSINDNEG2322247183403502510363398
31QFT - IT tests done at UIC 8/08 to 8/09 Total number of QTBGI tests done at UIC - 7,688Total number of positives - 612Total number of indeterminates - 155Total number of Negatives - 6,921
32Discordant results with QFT - Gold Total number of new positives that are on raw data sheet during this time: 8847 of the 88 cases had a positive PPD history, negative QTBG gold history and presently are positive In-tube at initial and repeat testing.Total from this number that went from 1st time positive and then negative at repeat testing: 2413 from this number had a positive PPD history11 from this number had a negative PPD history
33Higher sensitivity seen with QuantiFERON® TB-Gold “In Tube” A.R. PPD positive in past.QFT-2G: ESAT-6 CFP-10Neg 3/6/Pos 9/14/Neg 3/21/QTBG IN-TUBE TB-AgPos 9/4/Pos 10/30/
34Interpreting ResultsA general overview of the guidelines used at UICMCMust recognize some results (very small number, <1% at UICMC) must be reviewed in more detail on case by case basisSuccessful interpretation may involve collaboration between Employee Health Services, Laboratory, Infection Control, and/or Cellesitis; as well as, detail history from the employee
35Interpreting ResultsNegative – exposure to M. tuberculosis is unlikelyPositive – exposure to M. tuberculosis is likelyIndeterminate – results are inconclusive. Not a positive test.
36QFT negative regardless of PPD history Cleared for employmentQFT positive w/ negative PPDRepeat the QFT immediately and do TB QuestionnairePositiveChest X-rayReferral to PCP for evaluationFuture testing to be determinedNegative – Annual or semi-annual Surveillance depending on departmentNotify lab to get raw data
37Indeterminate Results at Pre-Employment Screening Repeat QFT at time of annual or semi-annual testingCertain percentage of the population (very small number) are repeatedly IndeterminateContinue Surveillance on these employeesRemember Indeterminate results are NOT positive results
39REFERENCES http://www.cdc.gov/nchstp/tb/default.htm Guidelines for Using QuantiFERON-TB Gold Test for detecting Mycobacterium tuberculosis Infection, United States, MMWR December 16, 2005; 54.Guidelines for the Preventing the Transmission of Mycobacterium tuberculosis in Health-Care Settings, 2005, MMWR December 30, 2005;54.