Sensitivity and specificity of salivary pipecolic acid in head and neck squamous cell carcinoma

Aim: The aim of the present preliminary case-control study was to test the sensitivity and specificity of salivary pipecolic acid in predicting head and neck squamous cell carcinoma (HNSCC). Methods: High-performance liquid chromatography was used for the analysis of non-stimulated saliva samples from 40 individuals: 20 in the case group (recently diagnosed with untreated HNSCC) and 20 in the control group (individuals without cancer). Both groups included patients taking daily oral hypoglycemic drugs (comorbidity). The case and control groups were matched at a proportion of 1:1 for sex and comorbidity. Results: Mean salivary levels of pipecolic acid were 169.38 ng/ mL in the case group and 114.66 ng/mL in the control group (p<0.001). Individuals who took oral hypoglycemic drugs had higher levels of pipecolic acid in both the case and control groups (p<0.001). The receiver operating characteristic curve analysis revealed 90% sensitivity and 65% specificity for head and neck cancer, with an area under the curve of 0.838 between the case and control groups. Conclusions: Pipecolic acid had high sensitivity for the diagnosis of HNSCC but low specificity in the sample analyzed. Our findings suggest that salivary pipecolic acid levels are associated with glucose homeostasis. Studies with larger samples are required to evaluate the specificity of this metabolite.