EBM - Diagnostic
Evidence-Based Medicine See a patient Ask a question Seek the best evidence Appraise that evidence Apply the evidence Moni...
<ul><li>Critical Appraisal  - Worksheet for critical appraisal </li></ul><ul><li>  - Software : CAT Maker </li></ul><ul><l...
<ul><li>Untuk menegakkan diagnosis diperlukan uji diagnosis: </li></ul><ul><ul><li>Pemeriksaan klinis </li></ul></ul><ul><...
<ul><li>Uji diagnostik yg ideal: uji yg memberi hasil positif pd semua subjek yg sakit dan memberikan hasil negatif pd sem...
<ul><li>Tujuan: </li></ul><ul><ul><li>Utk menegakkan diagnosis penyakit atau menyingkirkan penyakit (sensitif : kemungkina...
<ul><li>Prinsip dasar uji diagnostik: </li></ul><ul><li>Uji diagnostik baru hrs memberi manfaat yg lebih dibanding uji dia...
<ul><li>Pd uji diagnostik kita menentukan bagaimana suatu uji dpt memisahkan antara subjek yg sakit dgn yg tdk sakit.  </l...
Total 200 PS+NB 100 PB+NS 100 Jlh NB+NS NB 70 NS 35 Negatif PB+PS PS 30 PB 65 Positif Hasil uji Jlh Non limfoma Limfoma Pe...
SENSITIVITAS dan SPESIFISITAS TABEL 2X2 HASIL UJI DIAGNOSTIK YAITU HASIL YG DIPEROLEH DGN UJI YG DITELITI DAN DGN HASIL PD...
<ul><li>PRE-TEST PROBABILITY  = PREVALENCE  =  (A+C   ) / (A+B+C+D) </li></ul><ul><li>LR = LIKELIHOOD RATIO </li></ul><ul>...
<ul><li>Sensitivitas:  </li></ul><ul><ul><li>memperlihatkan kemampuan alat diagnostik utk mendeteksi penyakit. </li></ul><...
<ul><li>Positive Predictive Value:  </li></ul><ul><ul><li>Probabilitas seseorang menderita penyakit apabila uji diagnostik...
<ul><li>Likelihood ratio: </li></ul><ul><ul><li>Probabilitas dari hasil test pad orang yang menderita penyakit dibandingka...
<ul><li>POSITIVE LIKELIHOOD RATIO (LR+)  </li></ul><ul><li>Menunjukkan berapa besar kemungkinan suatu test memberikan hasi...
Kemampuan suatu test yang valid, bila dapat merubah pendapat kita dari apa yang kita pikirkan sebelum test (pretest probab...
Sensitivitas = A : (A+C) = 65 : 100 = 65% Spesifisitas = D : (B+D) = 70 : 100 = 70% Uji diagnostik terbaik adalah uji diag...
Cth 2: 48 32 16 Jlh 31 28 3 Negatif 17 4 13 Positif Mammografi Jlh Non Ca Ca  Histopatologi SENSITIVITY:  A/(A+C) SPESIFIC...
Pretest probability  Post test probability 33.3%  76.4%    Diagnostic tests that produce  big changes  from pretest to po...
Worksheet for  Diagnosis
DIAGNOSIS WORKSHEET Are the results of this diagnostic study  valid ?  Citation: Was the test (or cluster of tests) valida...
Are the valid results of this diagnostic study  important ? SAMPLE CALCULATIONS Sensitivity = a/(a+c)  = 731/809 = 90% Spe...
Can you  apply  this valid, important evidence about  a diagnostic test in caring for your patient? Additional notes: Woul...
<ul><li>Software:  CAT Maker…… </li></ul>
<ul><li>Thank you….. </li></ul>
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Crp5.5 ebm-diagnosis

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Crp5.5 ebm-diagnosis

  1. 1. EBM - Diagnostic
  2. 2. Evidence-Based Medicine See a patient Ask a question Seek the best evidence Appraise that evidence Apply the evidence Monitor the change
  3. 3. <ul><li>Critical Appraisal - Worksheet for critical appraisal </li></ul><ul><li> - Software : CAT Maker </li></ul><ul><li> Main area of clinical objectives: </li></ul><ul><ul><li>1. Diagnosis </li></ul></ul><ul><ul><li>2. Prognosis </li></ul></ul><ul><ul><li>3. Therapy/Treatment </li></ul></ul><ul><ul><li>4. Risk/Harm </li></ul></ul><ul><li> Others: </li></ul><ul><ul><li>Systematic Review and Meta-analysis </li></ul></ul><ul><ul><li>Clinical Guidelines </li></ul></ul><ul><ul><li>Clinical Decision Making etc. </li></ul></ul>
  4. 4. <ul><li>Untuk menegakkan diagnosis diperlukan uji diagnosis: </li></ul><ul><ul><li>Pemeriksaan klinis </li></ul></ul><ul><ul><li>Pemeriksaan lab sederhana </li></ul></ul><ul><ul><li>Pemeriksaan lain yg lbh canggih </li></ul></ul><ul><li>Uji diagnostik bisa dilakukan scr </li></ul><ul><ul><li>bertahap (serial): mis test tuberkulin dahulu baru foto thorak </li></ul></ul><ul><ul><li>Paralel: bbrp pemeriksaan dilaksanakan sekaligus. </li></ul></ul>
  5. 5. <ul><li>Uji diagnostik yg ideal: uji yg memberi hasil positif pd semua subjek yg sakit dan memberikan hasil negatif pd semua subjek yg tidak sakit. </li></ul><ul><li>Tetapi ada kemungkinan diperoleh hasil uji positif pd subjek yg sehat (false posititive) dan hasil negatif pd subjek yg sakit (false negative). </li></ul>
  6. 6. <ul><li>Tujuan: </li></ul><ul><ul><li>Utk menegakkan diagnosis penyakit atau menyingkirkan penyakit (sensitif : kemungkinan negatif semu kecil; spesifik : kemungkinan positif semu kecil) </li></ul></ul><ul><ul><li>Utk keperluan screening (mencari subjek yg asimptomatik) </li></ul></ul><ul><ul><li>Utk pengobatan pasien  memantau perjalanan penyakit, mengidentifikasi komplikasi, mengetahui kadar terapi suatu obat, menetapkan prognosis dan mengkonfirmasi suatu hasil pemeriksaan yg tak diduga </li></ul></ul><ul><ul><li>Utk studi epidemiologis </li></ul></ul>
  7. 7. <ul><li>Prinsip dasar uji diagnostik: </li></ul><ul><li>Uji diagnostik baru hrs memberi manfaat yg lebih dibanding uji diagnostik yg sdh ada. </li></ul><ul><ul><li>Lebih sederhana/mudah, murah dan tidak invasif </li></ul></ul><ul><ul><li>Dpt mendiagnosa pd fase lebih dini </li></ul></ul><ul><li>Uji diagnostik bbtk tabel 2x2: </li></ul>PB=positif benar ; PS = positif semu ; NS = negatif semu ; NB = negatif benar total PS+NB PB+NS Jlh NB+NS NB NS Tidak PB+PS PS PB Ya Hasil uji Jlh Tidak Ya Penyakit
  8. 8. <ul><li>Pd uji diagnostik kita menentukan bagaimana suatu uji dpt memisahkan antara subjek yg sakit dgn yg tdk sakit. </li></ul><ul><ul><li>Cth </li></ul></ul><ul><ul><li>Suatu uji diagnostik thd 100 pasien limfoma malignum yg dibuktikan dgn biopsi, 65 menunjukkan hasil positif; sdgkan uji diagnostik yg sama thd 100 pasien dgn pembesaran kelenjar non-limfoma, hanya 30 yg menunjukkan hasil uji positif. Bila dilakukan uji hipotesis dgn X 2, tdpt hubungan yg bermakna (p<0,001) antara hasil uji positif dgn tdptnya limfoma malignum. </li></ul></ul>
  9. 9. Total 200 PS+NB 100 PB+NS 100 Jlh NB+NS NB 70 NS 35 Negatif PB+PS PS 30 PB 65 Positif Hasil uji Jlh Non limfoma Limfoma Penyakit
  10. 10. SENSITIVITAS dan SPESIFISITAS TABEL 2X2 HASIL UJI DIAGNOSTIK YAITU HASIL YG DIPEROLEH DGN UJI YG DITELITI DAN DGN HASIL PD PEMERIKSAAN DGN BAKU EMAS. Sensitivitas = A : (A+C) Spesifisitas = D : (B+D) Nilai prediksi positif (Positive Predictive Value ) = A : (A+B) Nilai prediksi negatif (Negative Predictive Value) = D : (C+D) A+B+C+D B+D A+C Jlh C+D D C Negatif A+B B A Positif UJI Jlh Negatif Positif BAKU EMAS
  11. 11. <ul><li>PRE-TEST PROBABILITY = PREVALENCE = (A+C ) / (A+B+C+D) </li></ul><ul><li>LR = LIKELIHOOD RATIO </li></ul><ul><li>LR+ = SENSITIVITY/(1-SPESIFICITY) </li></ul><ul><li>LR- = (1- SENSITIVITY)/SPESIFICITY </li></ul><ul><li>PRE TEST ODDS = PREVALENCE : ( 1- PREVALENCE) </li></ul><ul><li>POST TEST ODDS = PRE TEST ODDS X LR </li></ul><ul><li>POST TEST PROBABILITY = POST TEST ODDS : (1 + POST TEST ODDS) </li></ul>
  12. 12. <ul><li>Sensitivitas: </li></ul><ul><ul><li>memperlihatkan kemampuan alat diagnostik utk mendeteksi penyakit. </li></ul></ul><ul><ul><li>Kemungkinan bahwa hasil uji diagnostik akan positif bila dilakukan pd sekelompok subjek yg sakit. </li></ul></ul><ul><li>Spesifisitas </li></ul><ul><ul><li>Menunjukkan kemampuan alat diagnostik utk menentukan bahwa subjek tidak sakit </li></ul></ul><ul><ul><li>Kemungkinan bahwa hasil uji diagnostik akan negatif bila dilakukan pd sekelompok subjek yg sehat. </li></ul></ul>
  13. 13. <ul><li>Positive Predictive Value: </li></ul><ul><ul><li>Probabilitas seseorang menderita penyakit apabila uji diagnostiknya positif. </li></ul></ul><ul><ul><li>= A : (A+B) </li></ul></ul><ul><li>Negative Predictive Value: </li></ul><ul><ul><li>Probabilitas seseorang tidak menderita penyakit apabila uji diagnostiknya negatif. </li></ul></ul><ul><ul><li>= D : (C+D) </li></ul></ul>
  14. 14. <ul><li>Likelihood ratio: </li></ul><ul><ul><li>Probabilitas dari hasil test pad orang yang menderita penyakit dibandingkan dengan probabilitas dari hasil test pada orang yang tidak menderita penyakit. </li></ul></ul><ul><ul><li>Likelihood ratio ini menunjukkan berapa kali kemungkinan suatu hasil test dijumpai pada orang yang menderita penyakit diabndingkan dengan orang normal. </li></ul></ul>
  15. 15. <ul><li>POSITIVE LIKELIHOOD RATIO (LR+) </li></ul><ul><li>Menunjukkan berapa besar kemungkinan suatu test memberikan hasil positif pada orang yang sakit dibandingkan pada orang sehat. </li></ul><ul><ul><li>= { a/(a+c)} / {b/(b+d)} </li></ul></ul><ul><ul><li>= SENSITIVITY / (1- SPECIFICITY) </li></ul></ul><ul><li>NEGATIVE LIKELIHOOD RATIO (LR-) </li></ul><ul><li>Menunjukkan berapa besar kemungkinan suatu test memberikan hasil negatif pada orang yang sakit dibandingkan pada orang sehat. </li></ul><ul><ul><li>= { c/(a+c)} / {d/(b+d)} </li></ul></ul><ul><ul><li>= (1- SENSITIVITY ) / SPECIFICITY </li></ul></ul>
  16. 16. Kemampuan suatu test yang valid, bila dapat merubah pendapat kita dari apa yang kita pikirkan sebelum test (pretest probability) ke apa yang kita pikirkan setelah test (postest probability) Test diagnostic akan lebih berguna bila test tsb menghasilkan perubahan yang besar (big changes) dari pretest probability ke postest probability.
  17. 17. Sensitivitas = A : (A+C) = 65 : 100 = 65% Spesifisitas = D : (B+D) = 70 : 100 = 70% Uji diagnostik terbaik adalah uji diagnostik yg mempunyai sensitivitas dan spesifisitas yg tertinggi Cth 1: 200 100 100 Jlh 105 70 35 Negatif 95 30 65 Positif Hasil uji Jlh Non limfoma Limfoma Penyakit
  18. 18. Cth 2: 48 32 16 Jlh 31 28 3 Negatif 17 4 13 Positif Mammografi Jlh Non Ca Ca Histopatologi SENSITIVITY: A/(A+C) SPESIFICITY: D/(B+D) LR+: SENS/ (1-SPEC) LR-: (1-SENS) /SPEC PRE-TEST PROBABILITY = PREVALENCE : (A+C ) / (A+B+C+D) (13/16)X100% = 81,25% (28/32)X100% =87,5% (13/16) /(1 - 28/32) =6,5 1-(13/16) /(28/32) =0,21 16/48 = 33,3%
  19. 19. Pretest probability Post test probability 33.3% 76.4%  Diagnostic tests that produce big changes from pretest to post-test probabilities are important and likely to be useful to us in our practice PRE TEST ODDS = PREVALENCE: (1-PREVALENCE) POST TEST ODDS = PRE TEST ODDS X LR+ P OST -TEST PROBABILITY= POST TEST ODDS: (1+POST TEST ODDS) (16/48) : (1-16/48) = 0,5 0,5 X 6,5 = 3,25 3,25 : (1+3,25) = 0.764 = 76,4%
  20. 20. Worksheet for Diagnosis
  21. 21. DIAGNOSIS WORKSHEET Are the results of this diagnostic study valid ? Citation: Was the test (or cluster of tests) validated in a second, independent group of patients? Was the reference standard applied regardless of the diagnostic test result? Was the diagnostic test evaluated in an appropriate spectrum of patients (like those in whom it would be used in practice)? Was there an independent, blind comparison with a reference (“gold”) standard of diagnosis?
  22. 22. Are the valid results of this diagnostic study important ? SAMPLE CALCULATIONS Sensitivity = a/(a+c) = 731/809 = 90% Specificity = d/(b+d) = 1500/1770 = 85% Likelihood ratio for a positive test result = LR+ = sens/(1-spec) = 90%/15% = 6 Likelihood ratio for a negative test result = LR - = (1-sens)/spec = 10%/85% = 0.12 Positive Predictive Value = a/(a+b) = 731/1001 = 73% Negative Predictive Value = d/(c+d) = 1500/1578 = 95% Pre-test probability (prevalence) = (a+c)/(a+b+c+d) = 809/2579 = 32% Pre-test odds = prevalence/(1-prevalence) = 31%/69% = 0.45 Post-test odds = pre-test odds  LR Post-test probability = post-test odds/(post-test odds +1) 2579 a+b+c+d 1770 b+d 809 a+c Totals 1578 c+d 1500 d 78 c Negative (  65 mmol/L) 1001 a+b 270 b 731 a Positive (< 65 mmol/L) Diagnostic test result (serum ferritin) Absent Present Totals Target disorder (iron deficiency anemia)
  23. 23. Can you apply this valid, important evidence about a diagnostic test in caring for your patient? Additional notes: Would the consequences of the test help your patient? <ul><li>Will the resulting post-test probabilities affect your management and help your patient? </li></ul><ul><li>Could it move you across a test-treatment threshold? </li></ul><ul><li>Would your patient be a willing partner in carrying it out? </li></ul><ul><li>Can you generate a clinically sensible estimate of your patient’s pre-test probability (from personal experience, prevalence statistics, practice databases, or primary studies)? </li></ul><ul><li>Are the study patients similar to your own? </li></ul><ul><li>Is it unlikely that the disease possibilities or probabilities have changed since the evidence was gathered? </li></ul>Is the diagnostic test available, affordable, accurate, and precise in your setting?
  24. 24. <ul><li>Software: CAT Maker…… </li></ul>
  25. 25. <ul><li>Thank you….. </li></ul>

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