Study limitations include the retrospective design, data obtained from a single centre possibly being biased for patients with more severe AGA, lack of blinding and proper control, and operator-dependent variation in hair counting. Although PRP is reported as a monotherapy for AGA, it is likely that patients are using multiple treatment modalities by the time they or their physician decide to pursue adjuvant PRP. Hair specialists disagree on the number of PRP treatments needed before assessing clinical efficacy; 1,3 however, these arguments are often based on anecdotes. Our data reveal that it is possible to use quantitative trichoscopy to stratify therapeutic response to adjuvant PRP after two treatment sessions (i.e. 2 months after initial PRP injections). Many factors affecting PRP efficacy and treatment response (e.g. platelet and growth factor concentration, leucocyte content, platelet activation, centrifugation protocols, total treatment sessions, duration between sessions, and maintenance therapy) are unknown, and it is possible that initial 'nonresponders' may respond to PRP therapy with continued sessions. Future directions include further characterization of patient response to adjuvant PRP based on response to prior AGA therapies, disease duration prior to PRP initiation, and the amount of PRP delivered per treatment. We hope our findings will help physicians counsel patients on the therapeutic benefit(s) of adjuvant PRP, and inform patient decisions regarding further treatment.