Table 1Major Outcomes of Interest

ComparatorsMagnitude of Effect; Risk/Odds (95% CI), NNT/NNH, SOE
DVTProximal DVTSymptomatic VTEPEMajor BleedingMinor Bleeding
Pharmacological prophylaxis vs. no prophylaxisDecreased risk by 44%; RR 0.56 (0.47 to 0.68), NNT 3 to 33 Image clinvtefu2.jpgDecreased risk by 47%; RR 0.53 (0.39 to 0.74), NNT 4 to 213 Image clinvtefu1.jpgNRNo difference; OR 0.38 (0.13 to 1.07) Image clinvtefu3.jpgNo difference; RR 0.74 (0.36 to 1.51) Image clinvtefu2.jpgRelative risk is higher for prophylaxis by 67%; RR 1.67 (1.18 to 2.38), NNH 30 to 75 Image clinvtefu1.jpg
LMWH vs. UFHDecreased risk by 20%; RR 0.80 (0.65 to 0.99), NNT 12 to 100 Image clinvtefu2.jpgDecreased risk by 40%; RR 0.60 (0.38 to 0.93), NNT 14 to 50 Image clinvtefu1.jpgNRDecreased odds by 52%; OR 0.48 (0.24 to 0.95), NNT 8 Image clinvtefu2.jpgDecreased odds by 35%; OR 0.57 (0.37 to 0.88), NNT 41 Image clinvtefu1.jpgNo difference; RR 0.90 (0.63 to 1.28) Image clinvtefu2.jpg
Enoxaparin vs. fondaparinuxRelative risk is higher for enoxaparin by 99%; RR 1.99 (1.57 to 2.51), NNH 13 to 26 Image clinvtefu2.jpgOdds are higher for enoxaparin by 219%; OR 2.19 (1.52 to 3.16), NNH 44 to 122 Image clinvtefu3.jpgNo difference; OR 0.70 (0.48 to 1.02) Image clinvtefu3.jpgNo difference; OR 3.34 (0.58 to 19.32) (SOE not rated)Decreased odds by 35%; OR 0.65 (0.48 to 0.89), NNT 74 to 145 Image clinvtefu2.jpgDecreased odds by 43%; OR 0.57 (0.35 to 0.94), NNT 31 to 60 Image clinvtefu3.jpg
LMWH vs. warfarinDecreased risk by 34%; RR 0.66 (0.55 to 0.79), NNT 6 to 13 Image clinvtefu3.jpgNo difference; RR 0.63 (0.39 to 1.00) Image clinvtefu3.jpgNo difference; OR 1.00 (0.69 to 1.46) Image clinvtefu3.jpgNo difference; OR 1.11 (0.57 to 2.19) Image clinvtefu2.jpgOdds are higher for LMWH by 92%; OR 1.92 (1.27 to 2.91), NNH 57 to 220 Image clinvtefu1.jpgRelative risk is higher for LMWH by 23%; RR 1.23 (1.06 to 1.43), NNH 18 to 218 Image clinvtefu2.jpg
UFH vs. desirudinRelative risk is higher for UFH by 231%; RR 2.31 (1.34 to 4.00), NNH 5 to 11 Image clinvtefu2.jpgOdds are higher for UFH by 477%; OR 4.74 (2.99 to 7.49), NNH 11 Image clinvtefu2.jpgNRNo difference; OR 3.23 (0.56 to 18.98) Image clinvtefu3.jpgNRNR
Prolonged vs. standardduration prophylaxisDecreased risk by 63%; RR 0.37 (0.21 to 0.64), NNT 5 to 32 Image clinvtefu2.jpgDecreased risk by 71%; RR 0.29 (0.16 to 0.52), NNT 9 to 71 Image clinvtefu1.jpgDecreased risk by 62%; RR 0.38 (0.19 to 0.77), NNT 8 to 54 Image clinvtefu2.jpgDecreased odds by 87%; OR 0.13 (0.04 to 0.47), NNT 24 to 232 Image clinvtefu1.jpgNo difference; OR 2.18 (0.73 to 6.51) Image clinvtefu3.jpgOdds are higher for prolonged prophylaxis by 244%; OR 2.44 (1.41 to 4.20), NNH 11 to 118 Image clinvtefu1.jpg
Pharmacological + mechanical vs. pharmacological onlyDecreased risk by 52%; RR 0.48 (0.32 to 0.72), NNT 3 to 67 Image clinvtefu2.jpgNo difference; RR 0.33 (0.09 to 1.22) Image clinvtefu3.jpgNRNo difference; OR 1.03 (0.14 to 7.34) Image clinvtefu3.jpgNRNR

95% CI = 95-percent confidence interval; DVT = deep vein thrombosis; LMWH = low-molecular-weight heparin; major bleeding (e.g., bleeding leading to greater transfusion requirements and/or reoperation); minor bleeding (e.g., surgical site bleeding, bleeding leading to infection, or bleeding leading to transfusion but not reoperation); NNH = number needed to harm (the calculated range); NNT = number needed to treat (the calculated range); NR = not reported or insufficient evidence to permit conclusions; OR = odds ratio; PE = pulmonary embolism; SOE = strength of evidence rating; THR = total hip replacement surgery; TKR = total knee replacement surgery; UFH = unfractionated heparin; VTE = venous thromboembolism

Strength of Evidence Scale

High: Image clinvtefu1.jpgThere is high confidence that the evidence reflects the true effect. Further research is very unlikely to change our confidence in the estimate of effect.
Moderate: Image clinvtefu2.jpgModerate confidence that the evidence reflects the true effect. Further research may change our confidence in the estimate of effect and may change the estimate.
Low: Image clinvtefu3.jpgLow confidence that the evidence reflects the true effect. Further research is likely to change our confidence in the estimate of effect and is likely to change the estimate.
Insufficient: Image clinvtefu4.jpgEvidence either is unavailable or does not permit estimation of an effect.

From: Venous Thromboembolism Prophylaxis in Orthopedic Surgery

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Comparative Effectiveness Review Summary Guides for Clinicians [Internet].

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