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DIAGNOSTIC VALUE of MEDICAL MICROBIOLOGY

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The program file has been made with the vision for basic responsibilities of the Medical Microbiologists for optimal decisions in Diagnostic Microbiology, Every specimen reflects the scenario in the ongoing process of infection in the human body ( from vivo to vitro) , However it is important to know the predictive value of the tests we do in the laboratory or else the blind processing will certainly harmful if not useful Dr.T.V.Rao MD
doctortvrao@gmail.com

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DIAGNOSTIC VALUE of MEDICAL MICROBIOLOGY

  1. 1. DIAGNOSTIC VALUE of MEDICAL MICROBIOLOGY Dr.T.V.Rao MD 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 1
  2. 2. Read the Program with a Purpose Every specimen needs optimal testing with vision of scientific basis • The program file has been made with the vision for basic responsibilities of the Medical Microbiologists for optimal decisions in Diagnostic Microbiology, Every specimen reflects the scenario in the ongoing process of infection in the human body ( from vivo to vitro) , However it is important to know the predictive value of the tests we do in the laboratory or else the blind processing will certainly harmful if not useful Dr.T.V.Rao MD21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 2
  3. 3. Purpose of Diagnostic Test in Diagnostic Microbiology• A diagnostic test for an infectious agent can be used to demonstrate the presence or absence of infection, or to detect evidence of a previous infection (for example, the presence of antibodies). Demonstrating the presence of the infecting organism, or a surrogate marker of infection, is often crucial for effective clinical management and for selecting other appropriate disease control activities such as contact tracing. 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 3
  4. 4. Role of microbiology laboratory: Introduction The diagnosis of infections performed by the laboratory has two important functions •Clinical • Diagnosis of infection in an individual patient for everyday management of infections •Epidemiological • Support for infection prevention and control in searching for source and route of transmission of HAI 21-10-2016 4Dr.T.V.Rao MD @Diagnostic Microbiology
  5. 5. Minimal requirements for microbiology services 1. Set up inside the facility • If not possible, negotiate a contract for diagnostic microbiology with the nearest laboratory 2. Available every day, including Sundays and holidays • Ideally on a 24-hour basis 3. Able to examine blood, cerebrospinal fluid, urine, stool, wound exudate or swab, respiratory secretions, and perform basic serological tests (HIV, HBV, HCV) 21-10-2016 5Dr.T.V.Rao MD @Diagnostic Microbiology
  6. 6. Minimal Requirements for microbiology services - 4. Identify common bacteria and fungi to species level 5. Perform susceptibility testing using disc- diffusion methodology 6. Perform basic phenotyping • Serotyping • Salmonellae, Shigellae, P. aeruginosa, N. meningitidis • Bio typing • S. typhi Shigella spp 21-10-2016 6Dr.T.V.Rao MD @Diagnostic Microbiology
  7. 7. Clinical role: Diagnosis of infectionDiagnosis should be rapid and accurate to the species level wherever possible • Classical bacteriological methods • Direct smear • Culture • Antigen detection • Sensitivity testing • Antibody detection • Not very useful in the early stages of infection • Molecular methods • Rarely used in routine work for the diagnosis of bacterial HAI 21-10-2016 7Dr.T.V.Rao MD @Diagnostic Microbiology
  8. 8. Bio Safety First •The investigators must comply with national workplace safety guidelines with regard to the safety of clinic and laboratory personnel and the disposal of infectious 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 8
  9. 9. WHY EARLY DIAGNOSIS • Early diagnosis and treatment can have an important role in preventing the development of long-term complications or in interrupting transmission of the infectious agent. • E.g. Tuberculosis • Influenza 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 9
  10. 10. Technological advances influences Diagnostic Microbiology •Recent technological developments have led to the proliferation of new, rapid diagnostic tests that hold promise for the improved management and control of infectious diseases. 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 10
  11. 11. We must learn which test is Optimal • Whether these tests are useful in a given setting and, if so, which test is most appropriate are questions that can be answered only through evaluations in the appropriate laboratory, clinical or field settings. 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 11
  12. 12. Preparing SOPs •SOPs should be prepared for for all clinical and laboratory procedures required in the study 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 12
  13. 13. All tests must executed with a purpose • Evaluations of diagnostic tests must be planned with respect to their use for a clearly defined purpose, carefully and systematically executed, and must be reported in a way that allows the reader to understand the study methods and the limitations involved and to interpret the results correctly. 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 13
  14. 14. Developing a plan for the study logistics • A plan should be developed for safe specimen collection, handling, transport and storage. Consider using pre-printed unique study numbers for forms and specimens Also, develop a flow diagram for specimen handling that can be distributed to laboratory staff.21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 14
  15. 15. Labelling the specimens are a must or just refuse the specimens • labels should be tested for adherence when samples are frozen, if necessary 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 15
  16. 16. Good sample Management a great Boon to success 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 16
  17. 17. Flow Chart of Laboratory Management of Clinical specimens 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 17
  18. 18. Why the laboratory Needs Clinical Information •No laboratory test is complete without a clinical Information •No interpretation has any clinical value if the clinical information is not taken into consideration 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 18
  19. 19. Clinicians too should understand the limitation of the tests Must be reported in a way that allows the reader to understand the study methods and the limitations involved and to interpret the results correctly. 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 19
  20. 20. Principles of Diagnostic value specimen 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 20
  21. 21. Performance characteristics • The basic performance characteristics of a test designed to distinguish infected from uninfected individuals are sensitivity, that is, the probability that a truly infected individual will test positive, and specificity, that is, the probability that a truly uninfected individual will test negative. These measures are usually expressed as a percentage. 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 21
  22. 22. Think about Sensitivity and Specificity of the test Results • Sensitivity and specificity are usually determined against a reference standard test, sometimes referred to as a 'gold standard' test, that is used to identify which subjects are truly infected and which are uninfected. 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 22
  23. 23. WHAT YOU UNDERSTAND BY GOLD STANDARD • Errors in measuring the sensitivity and specificity of a test will arise if the 'gold standard' test itself does not have 100% sensitivity and 100% specificity, which is not infrequently the case. Evaluating a diagnostic test is particularly challenging when there is no recognized reference standard test. 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 23
  24. 24. No test can performed well without knowing the Predictive Values • Two other important measures of test performance are positive predictive value (PPV), the probability that those testing positive by the test are truly infected, and negative predictive value (NPV), the probability that those testing negative by the test are truly uninfected. 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 24
  25. 25. What is composite reference standard • New tests under evaluation that are more sensitive than the existing reference standard usually require a composite reference standard. If a reference standard is not available and a composite standard cannot be constructed, an appropriate approach might be to report the levels of agreement between different tests, that is, positive by both or negative by both. 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 25
  26. 26. Reporting and disseminating results • It is imperative that these new diagnostics are rigorously and properly evaluated in the situations in which they will be deployed in disease control before they are released for general use. 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 26
  27. 27. Poorly performed Test is Harmful in clinical care • A poorly performing diagnostic might not only waste resources but might also impede disease control. The basic procedures described in this article for designing and conducting diagnostic evaluations provide an outline for ensuring the proper evaluation of new diagnostics in laboratory and field trials. 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 27
  28. 28. Role in prevention and control of healthcare associated infections •Outbreak investigation •Surveillance of HAIs •Alert microorganisms reports • Designing antibiotic policy21-10-2016 28Dr.T.V.Rao MD @Diagnostic Microbiology
  29. 29. Outbreak Investigation • To determine the cause of a single-source outbreak the causative agent must be defined • Then microbiology laboratory determines if two or more isolated strains are same or different 21-10-2016 29Dr.T.V.Rao MD @Diagnostic Microbiology
  30. 30. Additional tests during an outbreak • Sometimes the IP&C Team requires additional data to clarify endemic or epidemic situations • Microbiological tests may be required • Blood products • Environmental surfaces • Disinfectants and antiseptics • Air • Water • Hands of personnel • Anterior nares of personnel 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 30
  31. 31. 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 31
  32. 32. HAI surveillance • The microbiology laboratory should produce routine reports of bacterial isolates • Allows the IPC& Team to make graphs for specific pathogens, wards, and groups of patients • A ‘baseline incidence’ can be established • Any new isolate can then be compared with this incidence • If the laboratory is computerised, these data can be made readily available 21-10-2016 32Dr.T.V.Rao MD @Diagnostic Microbiology
  33. 33. Alert organism reports •Identify possible agreed ‘alert’ microorganisms • Methicillin-resistant Staphylococcus aureus (MRSA) • Vancomycin-intermediate S.aureus (VISA) • Vancomycin-resistant enterococci (VRE) • MDR Pseudomonas aeruginosa • MDR Acinetobacter baumannii • MDR Mycobacterium tuberculosis • ESBL enter bacteria • Clostridium difficile 21-10-2016 33Dr.T.V.Rao MD @Diagnostic Microbiology
  34. 34. Antibiotic policy • Regular reporting of changing resistance patterns –Newsletters –Specialty specific data • Restricted antibiotic reporting • Routinely only first line antibiotics • Reserve antibiotics only if pathogen is resistant to first line antibiotics21-10-2016 34Dr.T.V.Rao MD @Diagnostic Microbiology
  35. 35. Antibiotic stewardship Role of Clinical Microbiologist/ID specialist • Provide leadership to antimicrobial team • Antibiotic ward rounds • Interpretation of patient specific data to optimise treatment • culture & sensitivity • Active surveillance/ awareness • Screening for carriage of resistant bacteria • Molecular detection and typing 21-10-2016 35Dr.T.V.Rao MD @Diagnostic Microbiology
  36. 36. Interpretation of Microbiology Data •Microbiologists interpret microbiological data for IP&C staff •Results of isolation, identification, susceptibility tests, typing •Ideally should be medical doctor specialistt •If this is not possible, then a properly educated scientist is required21-10-2016 36Dr.T.V.Rao MD @Diagnostic Microbiology
  37. 37. Role in education • Infection prevention staff • how to interpret microbiological reports/charts • Other healthcare workers • specimen collection and transport, interpretation of reports and sensitivity tests • Students (medical and nursing) • basic microbiology 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 37
  38. 38. Please Visit me for more Clinical Microbiology topics • www.medmicrobes.com • www.slideshare.com • www.scribd.com • www.authourstream.com • Rao’s Microbiology and Rao’s infection on FACEBOOK • Google search for Infectious diseases by Dr.T.V.Rao MD 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 38
  39. 39. References • Evaluation of diagnostic tests for infectious diseases: general principles Shabir Banoo et al Reviews of Microbiology • GOOGLE resources on infectious diseases 21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 39
  40. 40. •Program Created by Dr.T.V.Rao MD for Medical and Paramedical Professionals for essential learning in Diagnostic Microbiology, as a part of open resource for New Generation Microbiologists •Email doctortvrao@gmail.com21-10-2016 Dr.T.V.Rao MD @Diagnostic Microbiology 40

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