In the 2021 study by Karantali et al. (26 RCTs), to investigate whether serum BDNF levels could be an optimal biomarker for predicting functional outcomes in acute stroke, the authors showed that acute stroke patients had significantly lower serum BDNF levels compared with healthy patients (overall analysis: SMD: −2.37, 95% CI: −4.36, −0.38; sensitivity analysis: SMD: −5.91, 95% CI: −8.40; −3.41, p < 0.0001, t2 = 10.55, I2 = 98.8%) and that the role of BDNF on functional outcome prediction in stroke patients is unclear [52]. The gene discussed is BDNF; the disease is stroke disorder.