1. EBM - Diagnostic

2. Evidence-Based Medicine See a patient Ask a question Seek the best evidence Appraise that evidence Apply the evidence Monitor the change

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. 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

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. 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. 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. 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. Worksheet for Diagnosis

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. 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)