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D.Vijay kumar Dist.Sales Manager Abbott Hyderabad.

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Presentation on theme: "D.Vijay kumar Dist.Sales Manager Abbott Hyderabad."— Presentation transcript:

1 D.Vijay kumar Dist.Sales Manager Abbott Hyderabad.
HIV TESTING PROTOCOLS D.Vijay kumar Dist.Sales Manager Abbott Hyderabad.

2 * HIV testing – voluntary Mandatory testing – counterproductive
Informed consent prior to testing is essential to deal with issues like- Confidentiality Discrimination Victimization Psychological harm * HIV testing – voluntary Mandatory testing – counterproductive

3 Purpose of HIV testing

4 Transfusion safety Epidemiological - Sentinel surveillance Diagnostic purpose Voluntary testing Research

5 PPTCT Pregnant HIV infected women can-
make informed decisions about dealing with pregnancy receive appropriate and timely interventions to decrease MTCT ensure safe delivery secure early access to HIV care and treatment educated in prevention of HIV transmission receive follow-up health care for self and child Pregnant HIV non infected women can be educated and counselled to remain uninfected

6 Serological Profile of HIV infection

7 Tests for detecting HIV INFECTION
Detection of specific antibodies screening tests: 100% sensitive supplemental/ confirmatory tests- sens. > 99.8% spec. > 98.5% Detection of specific antigens

8 Accuracy with which a test can confirm the presence of an infection.
SELECTION OF TESTS : BASED ON SENSITIVITY ,SPECIFICITY,EFFICIENCY,PPV & NPV Sensitivity – Accuracy with which a test can confirm the presence of an infection. Test with high sensitivity – few false negatives TP Sensitivity = x 100 TP + FN

9 SPECIFICITY- Accuracy with which the test can confirm the absence of an infection test with high specificity – few false positives used for diagnosing infection in an individual TN Specificity = X 100 TN + FP

10 Efficiency - ability of a test to correctly identify -
all positives as positives all negatives as negatives TP + TN Efficiency = X 100 TP + FN + TN + FP

11 Predictive values PPV – identifies ACTUALLY infected individuals TP X 100 TP + FP NPV – identifies ACTUAL non infected TN TN + FN

12 ELISA Most common screening test
Indirect solid phase enzyme linked immunosorbent assay/ EIA Used in blood banks/ tertiary labs Fourth generation ELISA decreases window period DISADVANTAGES Many false positives Few false negatives Time consuming Needs infrastructure & tech. expertise

Substrate Enzyme conjugated Anti-HIV antibody in specimen Antigen On solid phase

14 ELISA cont. False positives: auto immune diseases multiple pregnancies
hematologic malignancies primary biliary cirrhosis alcoholic hepatitis CRF False negatives window period immunosuppressive therapy malignant disorders late stage disease technical errors

15 Rapid tests Dot blot assay- immuno concentration method
Retroquic -line assay Tridot - dot assay Immunocomb assay – dipstick/comb ELISA based HIV comb coomb AIDS Immunochromatography – lateral flow assays Determine,Unigold,Hemastrip Particle aggluttination – Capillus,Serodia ELISA based - EIA

16 Comb AIDS NON-REACTIVE INVALID TEST Dot immunoassay for HIV 1&2 using
whole blood,serum or plasma. Comb with 8 teeth- Megenta red spot Synthetic& recombinant peptides used Two spots-- Control spot & test spot. NON-REACTIVE REACTIVE For HIV-1 &2 INVALID TEST

17 TRIDOT HIV 1 – gp 41, gp 120. HIV 2 – gp 36. Highly specific. C 1 2


19 HIV EIA Comb

HIV EIA Comb Rapid Visual EIA Test Detection of Antibodies to HIV-1 (including subgroups O & C) and HIV-2 Sensitivity (100%) Specificity (99.9%) INTERPRETATION OF RESULTS NON-REACTIVE HIV-1 HIV-2 HIV-1&2 REACTIVE INVALID TEST

21 SUPPLEMENTAL TESTS 1.Rapid tests. 2.Western blot. 3.Immunoblot.
4.Line immunoassay. WB/IB/LIA: highly specific but Expensive Labour intensive Needs expertise Equivocal/indeterminate results.

22 Western Blot for HIV Delineates the antibody profile of reactive serum
Used to grade intensity of ab response Qualitatively Quantitatively Procedure based on principle of ELISA WB Rotator platform WB strips

23 Western blot for HIV antibody
gp 36 Control band p 24 gp 31 gp 41 gp 120 & 160

Test – I: HIV Comb / Comb Aids – RS Test – II: Tridot / Retroquic Test – III: EIA Comb FOR SURVEILLANCE: BLOOD BANK: Only Test: Microlisa HIV

1.Screening ELISA/Rapid tests – used in strategy I, II, III. 2.Supplemental tests – E/R & Western Blot. Strategy I (for transfusion/transplantation safety) one test kit required AI A A positive negative

26 Strategy/Algorithm II A (for surveillance) 2 test kits required A1
A A Report negative A2 A1 + A A1+ A Report positive Report negative

27 Strategy/Algorithm II B (Diagnosis of an individual with AIDS indicator disease symptoms) test kits required A1 A A report negative A2 A1+ A A A report positive A3 A1+ A2 – A A1+ A2 - A indeterminate report negative

28 Strategy/Algorithm III To detect HIV infection in asymptomatic individuals (VCTCs, PPTCTs) test kits required A1 A A Report negative A2 A1+ A A1+ A2 – A3 A1+ A2+ A A1+ A2+ A A Report positive indeterminate A1+ A2- A A1+ A2- A Indeterminate report negative

29 INDETERMINATE STATUS: Repeat test after 14-28 days
INDETERMINATE STATUS: Repeat test after days Results continue to be indeterminate – WB/PCR refer to NRL. EQUIVOCAL WB: Rpt. WB after 2 weeks weeks weeks one year Correlate with high risk behaviour & clinical parameters.

P24 Antigen: Uncomplexed in serum, plasma, CSF, cell culture Indicates Active infection especially in newborn Resolves equivocal WB Window period CNS disease Immune collapse Monitoring response to ART. Method: EIA Disadvantages: Expensive Limited sensitivity Failure to detect HIV Failure to detect Ag when complexed with Antibody

31 Limitations of antigen detection methods
Not reliable Expensive Limited sensitivity-69% in patients with AIDS,15% in neonates Detection not possible in patients with high anti p24 antibody Cannot be used as a screening test

32 PCR Highly specific test-more than 95%
Highly sensitive-infants over 1 month Detects proviral DNA . Detects both latent viral infection and active viral transcriptipn. Detects viral load. Detects both HIV1 & HIV2.

Counselling for infant feeding & therapeutic intervention. First done at 6 weeks. Not Breast-fed, to say not infected: 2 negative test after 1 month (include 1 at 4 months) Not done as part of PPTCT in India. If symptoms occur at < 18 months: go for viral assays.

34 Diagnosing HIV infection in an infant born to HIV positive mother
Protocol 1 Asymptomatic 18 months-ELISA Non-reactive Reactive Conditionally consider confirm with a retest Non-infected Re-test NR HIV Unifected

Earlier than 12 mon defined symptoms Viral assay at 6 weeks same as for early Whenever symptoms occur symptoms Retest 1 month later If both are reactive consider reactive ELISA at 12 months Non reactive Reactive Follow protocol conditionally consider HIV +ve Retest at 18 months retest at 18 months Non reactive reactive HIV UNIFECTED HIV INFECTED

PARENT: Informed consent of the patient Pre n post test counselling Routine testing with three rapid tests first: highly sensitive test-NR-reported with exception of WP Indeterminate: 1st test reactive, 2nd/3rd NR repeat test after days WB/PCR: For persistent indeterminate cases. INFANT OF HIV + MOTHER, ASYMPTOMATIC: ELISA at 18 months—NR—Retest—NR—uninfected Reactive—consider infected, confirm with retest. INFANT OF HIV + MOTHER, SYMPTOMATIC: ELISA at 12 months—NR—retest NR—uninfected. Reactive—retest R at 18 months—infected.


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