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Diagnosis of AIDS

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AIDS continues to be important communicable disease.Optimal Diagnostic methods are a priority in Diagnosis..Errors in diagnosis can lead can be catostropic. consequences.

AIDS continues to be important communicable disease.Optimal Diagnostic methods are a priority in Diagnosis..Errors in diagnosis can lead can be catostropic. consequences.

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  • 1. Diagnosis of AIDS Dr.T.V.Rao, MD.
  • 2. AIDS A Global Concern
    • TODAY THERE IS NO REGION OF THE WORLD UNTOUCHED BY PANDEMIC OF
    • AIDS
  • 3. Majority of persons infected with HIV present with AIDS soon or later.
  • 4. Why AIDS is more important TODAY
    • Apart from Men, there is a increasing burden of Infections in Women.
    • Implication on Mother to Child Transmission
    • Female Adolescents are infected 3 - 6
    • times higher than male counterparts.
    • AIDS has turned out to be Social
    • Problem.
  • 5. Implication of AIDS
    • Being diagnosed as having HIV/AIDS has life time repercussions.
    • Every body understands AIDS as a life threatening condition.
    • A casual way of dealing as being HIV + will have Moral, Legal, and Social consequences.
  • 6. Prompt and Precise Diagnosis of AIDS make great impact on Humanity
  • 7. Importance of precise Diagnosis of AIDS
    • All patients should be informed about consequences of Testing for HIV infection,
    • Legality of respective National Laws should be followed.
    • A pretest and posttest counseling is Growing importance, even in Developing countries.
    • Today’s debate on testing for HIV status as matter of Health protocol ?
  • 8. Counseling Improves the confidence
  • 9. Purpose of Testing for HIV Infection
    • A matter of great importance as in Blood donors to prevent infected blood being transfused.
    • To diagnose the patients infected with HIV virus.
    • For surveillance purpose.
    • Persons with high risk behavior.
    • In Pregnant women to prevent Mother to Child transmission.
    • Patient's presenting with opportunistic infections.
  • 10. Diagnosis of HIV/ AIDS
    • Basic Tests.
    • 1.We can detect Antigen or Antibody
    • 2.We can detect Antigen and Antibody.
    • 3.Majority of Laboratories depend on Commercial Kits.
    • 4.Devloped Nations going for Molecular and more precise Methods.
  • 11. Screening Tests for HIV/AIDS Detection
    • A screening test posses high Sensitivity
    • We rarely miss the Diagnosis in Infected patients.
    • Done as mass screening procedure.
    • Economical.
    • Developing countries depend on these tests even
    • for Diagnosis.
  • 12. Confirmatory Tests in AIDS
    • It is important to confirm all screening tests with Confirmatory tests, or we brand some one without infection as infected,
    • Confirmatory tests differentiates false reactive tests. and identifies truly infected or not.
  • 13. Differences of Screening and Confirmatory Tests.
    • Screening test
    • High degree of Sensitivity
    • Few false negatives
    • Confirmatory test
    • High degree of specificity
    • Few / No false positive
    • results.
  • 14. Why patients should we tested with Screening and Confirmatory tests.
    • Before you declare a person infected with HIV / AIDS you should perform both methods.
    • Faulty testing methods can lead to catastrophic consequences, and legal litigations.
  • 15. Choosing Screening Testing methods
    • Our aim to obtain 100 % specific results ?
    • But impossible.
    • As few may be infected and do not have sufficient antibodies to detect in the testing methods.
    • Depend on time tested methods.
    • Explore the reputation of the suppliers.
  • 16. ELISA METHOD
    • Universally accepted test ,most popular even in the developing nations.
    • Useful in large scale screening.
    • A common method used in Blood banks in mass screening of Human blood.
  • 17. ELISA method – A ELISA plate
  • 18. Sequence of Events in ELISA test
  • 19. Different Methods of ELISA testing.
  • 20. Why ELISA is very trust worthy.
    • Easy to perform
    • Free from Radiation.
    • Relatively specific
    • Sensitive.
    • With scientific advances we have advanced to new generation of testing methods
    • Today we depend on 3 rd and 4 th generation ELISA methodologies.
  • 21. Significance of ELISA
    • Most reliable screening test for HIV infection.
    • 50% of the infected will show positive reactivity in < 22 days.
    • 95% show reactivity < 6 weeks
    • Sensitivity > 99.9 %
    • But needs confirmation with Western Blot.
  • 22. Advances in ELISA Methods.
    • 1 st and 2 nd generation ELISA methods have become obsolete we have to switch to
    • Antigen sandwich ELISA protocols ( called as 3 rd generation ELISA ).
    • Many Nations have switched to 3 rd generation methods.
  • 23. What is 3 rd Generation ELISA
    • Helps in detection of early infections,
    • Can detect all classes of antibodies including Ig M
    • All isotypes of antibodies can be captured.
    • But proving to be expensive to developing Nations.
  • 24. Need for 4 th Generation ELISA Methods The quest for better Diagnosis of AIDS continues
  • 25. What is 4 th generation ELISA.
    • A new generation Method in ELISA
    • Can detect both Antigen and Antibody in the same run ( in the same ELISA Plate )
    • Helpful to make early diagnosis at least in few cases.
  • 26. Determination of P 24 Antigen by ELISA
    • Helps in the early detection of HIV infection.
    • Screening of Blood for HIV infection along with detection for antibody detection.
    • Early diagnosis of HIV infection in resource poor nations.
    • Monitoring Anti-retroviral therapy. But not a replacement for RNA quantization.
    • Even P 24 Antigens are subject of false positive results.
  • 27. Limitation of Screening Tests.
    • Imperfect Sensitivity,
    • Sensitivity to detect HIV2 ?
    • Failing to detect HIV variants.
    • Other technical errors.
  • 28. Confirmatory Serological Tests All the Screening tests need to be confirmed before being declared as HIV infected.
  • 29. Confirmatory Serological Tests.
    • HIV Western Blots.
    • Line Immunoassay ( LIA )
    • Immuno fluorescent Assay ( IFA )
    • Utility is limited due technical and economical reasons
  • 30. WESTEN BLOT TEST
    • A Gold standard confirmatory test.
    • When tested combined with ELISA specificity is > 99.9 %.
  • 31. Relation of HIV structure and Western Blot configuration
  • 32. Principle of Western Blot
    • HIV viral antigens are separated as;
    • gp160,gp120,p66,p55,p51,gp41,p31,p24,
    • p17, and p15.
    • Interpretation depends on presence / absence of reactivity to specific antigens.
  • 33. Interpretation of Western Blot.
    • The antibodies in the serum should react with at least two of following antigens,
    • gp 160/120 If does not meet
    • gp 41 requirements, marked
    • p 24 as indeterminate.
  • 34. Negative Western Blot.
    • Absence of any reactivity to the
    • bands is declared as Negative.
    • False positives are rare.
    • All doubtful results should be
    • reported as Negative.
  • 35. Profile of Western Blot Test
  • 36. Limitation of Western Blot Test
    • If not designed for HIV 2 inclusion, we miss HIV2 infections,
    • Can give Indeterminate results in
    • Pregnancy
    • After administration of Tetanus
    • Toxoid.
    • Autoimmune conditions.
  • 37. Rapid tests in the Diagnosis of AIDS
    • A growing importance
    • Results can be issued within < 20 minutes.
    • Limited protocols, and less demanding technical skills.
    • But needs confirmation with ELISA / Western Blot testing.
    • Can differentiate HIV 1 and HIV 2.
  • 38. Rapid Testing for AIDS with Dot Methods
  • 39. Dot / Rapid Methods Useful
    • In patients in Labor whose Immune status is not known,
    • Resource poor establishments.
    • But needs confirmation with ELISA / WB
  • 40. Other supporting tests in AIDS Several tests will help in supporting to identify the progression of Disease.
  • 41. Flowcytometry for Estimation of CD 4 lymphocytes
  • 42. Use of CD 4 counts in Progress of AIDS
    • CD 4 count measurements help for staging the diseases.
    • Flow cytometry has become the prominent tool in estimations of CD 4.
    • Specimens should be promptly processed.
  • 43. Uses of Absolute CD4 Lymphocyte counts.
    • Most widely used predictor of HIV progression.
    • Risk of progression to an AIDS defining illness, opportunistic infections or malignancy is high, when the counts drop below 200/mcl.
  • 44. Uses of CD4 Lymphocyte percentage.
    • Estimation of percentages is more useful than CD4 counts.
    • When the counts drops < 20% we have to watch for onset of opportunistic infections and malignancy.
  • 45. Molecular Methods in Diagnosis of AIDS
  • 46. Molecular Methods in Diagnosis of HIV / AIDS.
    • 1. The reverse transcription polymerase
    • chain reaction.
    • 2. Nucleic acid sequence
    • amplification. ( NASBA )
    • 3. Branched chain DNA bDNA.
  • 47. DNA –PCR ( RT-PCR) popular among Molecular Method
  • 48. Polymerase Chain Reaction.-RT- PCR
    • RT-PCR Need the use of Reverse transcriptase enzyme that converts RNA to DNA.
    • The testing is based on artificially replicating Nucleic acid sequence
    • of the target ( viral sequence ) so that
    • Millions to Billions are made available
    • for detection.
  • 49.  
  • 50. HIV Viral Load tests.
    • The tests measure the amount of actively replicating HIV virus.
    • Correlates with response to antiretroviral drugs
    • Most helpful in diagnosis of HIV before Sero conversion.
    • False positives should be possible with low viremia < 500 copies.
  • 51. Alternative Testing Media. From other Specimens.
    • Saliva Detection of Ig G
    • Urine Detection of Ig G
    • Both ELISA and Western Blot
    • can be performed.
  • 52. Reporting of all Positive results is a great concern, Avoid casual reporting
  • 53. Post test counseling a Must in all Positive results
  • 54. Precautions in HIV Testing.
    • Casual testing to be curtailed.
    • To do with a purpose.
    • HIV positive result has Moral,social,and Economic consequences.
    • Post test counseling a must in all HIV+ individuals.
  • 55. AIDS is
    • Caused by fascinating Virus to - Scientists,
    • Friendly in approach to - Lovers.
    • Dangerous to Life to - Infected.
    • Dr.T.V.Rao,MD
  • 56. STOP AIDS.
    • Dr.T.V.Rao MD.
    • Professor of Microbiology
    • e mail [email_address]