## 3 Results
### Platelet-Rich Plasma Quality  
Fresh autologous whole blood was used as the source of PRP in all but one study [40]. The anticoagulants used for PRP procurement were sodium citrate (SC) in 8/22 (36.4%) studies [52; 53; 54; 18; 43; 50; 52; 54; 18], acid citrate dextrose (ACD) in 4/22 reports [17; 37; 44; 45] (18.17%), and citrate phosphate dextrose (CPD) in 3/22 registries [39; 40; 42] (13.50%), while no anticoagulant was reported in 8/22 (36.35%) studies [55; 38; 46; 47; 48; 49; 50; 51]. The volume of fresh whole blood (WB) collected across the studies for PRP preparation ranged from 15 mL to 300 mL, with most studies using 50-81 mL [17; 18; 37; 38; 39; 43; 45; 47; 52; 53]. However, 9/22 (40.90%) of the studies did not report the volume of WB used to produce PRP [42; 46; 48; 49; 50; 51; 54; 56; 42; 46; 47; 52; 54; 48; 53; 54; 55; 49; 60; 61; 62; 63; 64; 65; 66; 67; 68; 69; 70; 71; 72; 73; 74; 75; 76; 77; 78; 79; 80; 81; 82; 83; 84; 85; 86; 87; 88; 89; 90; 91; 92; 93; 94; 95; 96; 97; 98; 99; 100; 101; 102; 103; 104; 105; 106; 107; 108; 109; 110; 111; 112; 113; 114; 115; 116; 117; 118; 119; 120; 121; 122; 123; 124; 125; 126; 127; 128; 129; 130; 131; 132; 133; 134; 135; 136; 137; 138; 139; 140; 141; 142; 143; 144; 145; 146; 147; 148; 149; 150; 151; 152; 153; 154; 155; 156; 157; 158; 159; 160; 161; 162; 163; 164; 165; 166; 167; 168; 169; 170; 171; 172; 173; 174; 175; 176; 177; 178; 179; 180; 181; 182; 183; 184; 185; 186; 187; 188; 189; 190; 191; 192; 193; 194; 195; 196; 197; 198; 199; 200; 201; 202; 203; 204; 205; 206; 207; 208; 209; 210; 211; 213; 214; 215; 216; 217; 218; 219; 223; 224; 225; 226; 227; 228; 229; 230; 231; 232; 233; 234; 235; 236; 237; 238; 239; 240; 241; 242; 243; 244; 245; 246; 247; 248; 249; 250; 251; 252; 253; 254; 255; 256; 257; 258; 259; 260; 261; 262; 263; 264; 265; 266; 267; 268; 269; 270; 271; 272; 273; 274; 275; 276; 277; 278; 279; 280; 281; 282; 283; 284; 285; 286; 287; 288; 289; 290; 287; 289; 288; 289; 291; 280; 285; 286; 287; 289; 281; 288; 287; 288; 289; 292; 289; 293; 285; 286; 287; 289; 294; 288; 289; 295; 289; 300; 301; 302; 303; 304; 305; 306; 307; 308; 309; 310; 311; 312; 313; 314; 315; 316; 317; 318; 329; 336; 340; 319; 350; 351; 352; 353; 354; 355; 356; 357; 358; 359; 360; 371; 372; 373; 374; 375; 376; 377; 378; 389; 390; 391; 392; 393; 394; 395; 396; 397; 398; 40; 40; 40; 40; 40; 41; 41; 42; 43; 44; 45; 46; 47; 48; 49; 50; 51; 54]. The platelet concentration in PRP ranged from 100 \(\times\) 10\({}^{3}\) to 1370 \(\times\) 10\({}^{3}\) PLTS/\(\mu\)L, with most studies achieving between a 1.3- to 8.7-fold increase over baseline WB platelet counts. However, data for platelet enrichment in PRP was reported only in 9/22 (40.90%) studies [17; 37; 38; 39; 43; 45; 48; 50; 40; 41; 42; 43; 45; 48; 50]. On the other hand, only 9/22 (40.90%) studies reported the concentration of leukocytes in PRP [37; 38; 40; 45; 48; 50; 51; 55; 56]. In these studies, the leukocyte concentration in PRP ranged from 0.1 \(\times\) 10\({}^{3}\) to 42.1 \(\times\) 10\({}^{3}\) leukocytes/\(\mu\)L [40; 48; 50], with five studies [37; 48; 50; 56] classifying PRP as L-PRP and four studies [38; 40; 45; 51; 55] classifying PRP as P-PRP [20; 21]. Quality measures of PRP, such as a growth factor concentration determination, were reported only in 4/22 (18.18%) studies [18; 43; 48; 50]. The main mediators measured were TGF-\(\beta_{1}\), PDGF, VEGF, and IGF. On the other hand, 11/22 (50%) studies did not report whether PRP was activated or not at the time of its therapeutic or experimental application [37; 38; 40; 41; 42; 46; 47; 48; 50; 55]. PRP was injected without any activating agent in five studies [44; 45; 51; 54; 56], activated with calcium chloride in five studies [18; 39; 43; 52; 53], and activated with bovine thrombin in one study [17]. Of note, sodium bicarbonate was added to PRP as a buffer in one study [44]. PRP was injected intralesionally in all the studies. The volume of PRP administered ranged from 1 mL to 12 mL, with most studies using 2-5 mL per injection.