It can be diagnosed via blood study that identifies fat particles. The patient must fast overnight to prevent interference from fat in the blood due to food intake. The criteria for this (without the involvement of cholesterol-lowering drugs) are total cholesterol levels below 120 mg/dL and LDL cholesterol levels under 50 mg/dL.[1]
In the setting of critical illness, low cholesterol levels are predictive of clinical deterioration, and are correlated with altered cytokine levels.[2]
In humans with genetic loss-of-function variants in one copy of the ANGPTL3 gene, the serum LDL-C levels are reduced. In those with loss-of-function variants in both copies of ANGPTL3, low LDL-C, low HDL-C, and low triglycerides are seen ("familial combined hypolipidemia").[3]
Hooft disease is a rare condition evidenced by low blood lipid level, red rash and mental and physical retardation.[citation needed]
^The Merck Manual of Diagnosis of Therapy, 18th edition. 2006.
^Gordon BR, Parker TS, Levine DM, et al. (2001). "Relationship of hypolipidemia to cytokine concentrations and outcomes in critically ill surgical patients". Crit. Care Med. 29 (8): 1563–8. doi:10.1097/00003246-200108000-00011. PMID11505128.