Tuberculosis Contact Investigation in a Renal Dialysis Center: Blood Vs. Skin test

Size: px

Start display at page:

Download "Tuberculosis Contact Investigation in a Renal Dialysis Center: Blood Vs. Skin test"

Regina Berry
8 years ago
Views:

1 Tuberculosis Contact Investigation in a Renal Dialysis Center: Blood Vs. Skin test Kevin L. Winthrop M.D., M.P.H. Assistant Professor of Medicine Divisions of Infectious Diseases and Public Health and Preventive Medicine Oregon Health & Science University

Assistant Professor of Medicine Divisions of Infectious

2 TB and Renal Failure TB among dialysis patients 8-25 times higher rate (US and Canada) Chronic immune suppression Difficult diagnosis 40% extrapulmonary, often insidious Difficult screening 30-50% of patients with skin test anergy (candida, mumps, tetanus)

Difficult diagnosis 40% extrapulmonary, often insidious

3 Problems with Tuberculin Skin Test (TST) Poor inter-reader reliability False-positives/specificity NTM infection Prior BCG Poor positive-predictive value in low prevalence populations

4 Interferon-gamma Release Assays Use antigens highly specific for TB ESAT-6 and CFP-10 QuantiFERON-Gold (QFT-G) Measures INF-gamma release from lymphocytes incubated with TB antigen FDA-approved for the detection of LTBI, 2004 ELISPOT assay Measures # of reactive lymphocytes

release from lymphocytes incubated with TB antigen FDA-approved for

5 TB Case at Dialysis Center Foreign-born male Dialyzed MWF Pulmonary TB, AFB smear + Symptomatic with cough for one week Dialyzed daily last week before leaving center

7 Nurse s station

8 Study Enrollment Attempted to enroll all patients from first 3 daily shifts Contacts shared dialysis shift(s) during symptomatic period Non-contacts also enrolled Exclusion criteria History of LTBI treatment or TST >10mm

during symptomatic period Non-contacts also enrolled

9 Epidemiologic Methods Reviewed patient medical records Patients on MWF or TThS schedule 4 hour shifts Overlap with case noted Recent labs (albumin, CBC, BUN/CR, AST) TST screening history

10 Initial and Repeat Testing 11 weeks post-contact Blood drawn before dialysis began TST (Tubersol ) placed (read 48 hours later) Repeat testing at 16 weeks post-contact

11 Study Objectives Correlation of test results with exposure to TB case-patient Concordance between TST and blood tests Reproducibility of blood tests

12 Infection Case-definition Person testing positive on either initial or repeat testing TST >5mm QFT-G per kit ELISPOT Lewinsohn positive* * Mean number of spots from duplicate wells = 3 standard deviations greater than mean of media and greater than 10 spots

Lewinsohn positive* * Mean number of spots from duplicate wells

13 Proximity Measure of Contact Alternate contact measure taking into account seating proximity to case Trichotomous variable 0= non-contact 1= contact seated on other half of room 2= contact seated on same side

case Trichotomous variable 0= non-contact 1=

14 Statistical Methods Indeterminate results excluded QFT-G (n=2) ELISPOT (n=3) Logistic regression Univariate analysis of risk factors Multivariate model in stepwise backward fashion (variables with p<0.20 included)

Univariate analysis of risk factors Multivariate

15 Results 124 patients asked to enroll 12 declined (6 MWF, 6 TTH patients) 12 excluded with LTBI history No secondary cases of TB found Few tests turned positive between initial and repeat

16 Dialysis Patient Demographics by Contact Status (n=100) Contacts (n=58) Non-contacts (n=42) P-value Age* (range) 52 years (18-83) 60 years (19-90) 0.04 Sex 33 (57%) male 22 (53%) male 0.99 Foreign-born 31 (53%) 16 (38%) 0.13 *Median value

17 Dialysis Patients with LTBI by Test Test Contacts (n=58) Non-contacts (n=42) P-value TST+ 16 (28) 10 (24) 0.67 QFT-G+ 16 (29) 5 (13) 0.07 Elispot+ 20 (35) 7 (17) 0.05

18 Risk Factors for Positive TST Factor OR (95% CI) * P-value* Adj. P value ± Serum albumin 2.4 ( ) 0.19 N/A Foreign-birth 3.5 ( ) Contact 1.2 ( ) 0.67 N/A Increasing age 1.0 ( ) 0.91 N/A Recent TST 3.8 ( ) *From univariate analysis ± From a multivariate model incorporating all univariate risk factors with p-values <0.20 and age. TST performed previously in the study year

03) 0.91 N/A Recent TST 3.8 (1.3-11.2) 0.02 0.

19 Risk Factors for Positive QFT-G Factor OR (95% CI)* P-value* Adj. P-value ± Serum albumin 1.8 ( ) 0.40 N/A Foreign-birth 2.6 ( ) 0.07 N/A Contact 2.8 ( ) Increasing age 1.03 ( ) Recent TST 2.0 ( ) 0.19 N/A *From univariate analysis ± From multivariate model incorporating all univariate risk factors with p-values <0.20 and age TST performed previously in the study year

07) 0.05 0.01 Recent TST 2.0 (0.7-5.9) 0.

20 Risk Factors for Positive ELISPOT Factor OR (95% CI) * P-value* Adj. P-value ± Serum albumin 2.2 ( ) 0.24 N/A Foreign-birth 2.3 ( ) 0.08 N/A Contact 2.7 ( ) Age 1.00 ( ) 0.86 N/A Recent TST 1.9 ( ) 0.19 N/A *From univariate analysis ± From a multivariate model incorporating all univariate risk factors with p-values <0.20 and age TST performed previously in the study year

21 Proximity of Contact Persons sitting more closely were at increased risk QFT-G OR 2.3, 95% CI( ), adj. p=0.02 ELISPOT OR 2.2, 95% CI( ), adj. p= 0.01 TST No association

22 Reproducibility: Concordance of initial and repeat test results in dialysis patients* Test Concordance Kappa (95% CI) QFT-G 85% 0.57, 95% CI, Elispot 83% 0.61, 95% CI, *Considering all test outcomes (ex., positive, negative, indeterminate)

23 Concordance of Test Subject Results* TST QFT-2 Elispot TST ---- QFT-G 79% ---- Elispot 71% 87% *Evaluated by comparing concordance of test subject determination (infected or not-infected) using case definition

24 Conclusion QFT-G and ELISPOT Good agreement between More closely associated with TB exposure than TST Reproducibility was high Easy to perform in dialysis patients

25 Acknowledgements City of Long Beach Health Department Helene Calvet and EVERYONE California Department of Health Services Peter Oh, Melanie Lo, Travis Porco CDC Jerry Mazurek Cellestis Brenda Robles, Jim Rothel Oregon Health Sciences University David Lewinsohn, Melissa Nyendak, Lynn Swarbrick, Carol Johnson, Deborah Lewinsohn

26 TST positive / QFT-G negative 12 patients Univariate analysis (compared to those with concordant negative results): Factor OR (95% CI) P-value *Contact 0.9 ( ) 0.80 Age 1.0 ( ) 0.60 Foreign born 3.1 ( ) 0.09 Albumin 2.7 ( ) TST 2.3 ( ) 0.20 * Dichotomous variable (contact vs. non-contact)

27 TST positive / QFT-G negative Significantly more likely to be foreign born Due to NTM or BCG? Chance? Outcome not associated with age, albumin, or contact

28 TST Negative / QFT-G Positive 8 patients Univariate analysis (compared to those with concordant negative results): Factor OR (95% CI) P-value *Contact 6.0 ( ) 0.10 Age 1.05 ( ) 0.06 Foreign born 2.8 ( ) 0.18 Albumin 1.2 ( ) 0.84 *Dichotomous variable (contact vs. non-contact)

29 TST Negative / QFT-G Positive Multivariate analysis*: Factor Adj. OR (95% CI) P-value Contact 15.6 ( ) 0.03 Age 1.09 ( ) 0.02 *From model incorporating contact, age, and foreign birth.

30 TST Negative / QFT-G Positive Outcome significantly associated with increasing age and with contact Suggests QFT-2 could more sensitive in detecting infection

31 Elispot Positive/TST negative N=15 Not associated closely with anything

32 How QFT Works Stage 1 Whole Blood Culture Nil Control Avian PPD Human PPD Mitogen Control Heparinised whole blood Transfer undiluted whole blood into wells of a culture plate and add antigens Culture overnight at 37 o C TB infected individuals respond by secreting IFN-γ Stage 2 IFN-gamma ELISA Harvest Plasma from above settled cells and incubate 60 min in Sandwich ELISA COLOR TMB Wash, add Substrate, incubate 30 min then stop reaction Standard Curve OD 450nm Standard Curve IFN-γ IU/ml Measure OD and determine IFN-γ levels

33 Measuring T-cell Responses to TB Inject Tuberculin PPD Presenting cell T cell Cell recruitment & Activation release (IFN-gamma) Swelling at Injection Site

34 Dialysis Center Patient Demographics (n=100) Patients (n=104) Age* (range) 55 years (18-90) Sex 55 (55%) male Foreign-born 47 (47%) *Median value

35 Discussion QFT-2 and Elispot easier to perform in dialysis patients Blood drawn by tech Difficult to plant TST on some patients (skin fragility, graft placement)

Lisa Y. Armitige, MD, PhD has the following disclosures to make:

Interferon Gamma Release Assays (IGRAs) Lisa Y. Armitige, MD, PhD May 13, 2015 TB for Pulmonologist Phoenix, AZ March 13, 2015 EXCELLENCE EXPERTISE INNOVATION Lisa Y. Armitige, MD, PhD has the following