Analysis 2: HIT outcome (RCTs and prospective studies). Comparison: UFH versus LMWH; outcome (RCTs and prospective studies). Total events for treatment-LMWH = 1; for control-UFH = 31. Test for heterogeneity: χ² = 1.18, df = 4(P = .88), I² = 0%. Test for overall effect: Z = 3/74 (P < .001). Symbols are as in Figure 2.