The included studies utilized different types of malnutrition screening and diagnostic tools, including nutritional risk screening (NRS2000); nutritional status control (CONUT); mini nutritional assessment (MNA); Geriatric Nutritional Risk Index (GNRI); nutritional risk index (NRI); prognostic nutritional index (PNI); anthropometry (body mass index, upper arm circumference, Skinfold thickness); and biomarkers (albumin, lymphocyte count). The gene discussed is ALB; the disease is malnutrition.