Abstract: ObjectiveTo explore a better method to adjust platelet counts for light transmission aggregometry (LTA). MethodsBlood samples from 36 healthy participants aged from 18 to 50 yr. were collected.Platelet-rich plasma (PRP) was diluted using platelet-poor plasma (PPP) and physiological saline (PS), respectively, in a ratio of 1.5, 2, 2.5 and 3 times. Platelet aggregation was induced by adenosine diphosphate (ADP), arachidonic acid (ARA), collagen (COL), epinephrine (EPI), or ristocetin (RIS). The maximal aggregation rates (MAs) of different approaches were compared. We also compared the MAs induced by RIS between PRP-obtained-PPP and whole blood-obtained-PPP (2 100×g, 5 min). ResultsCompared with the original PRP, the MAs induced by ADP, ARA, and EPI decreased in PPP-adjusted PRP (significant at 2-3 times dilution ratio, P<0.05), but not in PS-adjusted PRP (P>0.05). The MA induced by RIS decreased in PS-adjusted PRP (significant at all dilution ratios, P<0.05), but not in PPP-adjusted PRP (P>0.05). No changes in the MA induced by COL were found in PS-adjusted PRP and PPP-adjusted PRP (P>0.05). Whole blood-obtained-PPP (2 100×g, 5 min) had the same MA induced by ristocetin compared with PRP-obtained-PPP (P>0.05). ConclusionPS is recommended for adjusting platelets counts for platelet aggregation induced by ADP, ARA, COL and EPI. Whole blood-obtained-PPP (2 100 ×g, 5 min) is recommended for RIS-induced aggregation as a matter of convenience.