II. Pathophysiology
- Cancer Antigen 19-9 is expressed in pancreatic disease and hepatobiliary disease
- CA 19-9 is a soluble, fucosylated glycosphingolipid CarbohydrateAntigen
- Structurally related to the Lewis Blood Group Antigens
III. Indications
- Pancreatic ductal adenocarcinoma
- Confirms diagnosis when consistent with other findings (see other False Positive causes below)
- Predicts prognosis as well as recurrence risk
- CA 19-9 level reduction by at least 50% after treatment is associated with a better prognosis
- Ye (2020) Cancer Chemother Pharmacol 86(6):731-40 +PMID: 33047181 [PubMed]
- Not indicated for screening in asymptomatic patients
- No tumor specific (see efficacy below)
IV. Causes: Increased CA 19-9
- Pancreatic Ductal Adenocarcinoma
- Chronic Pancreatitis
- Non-cancerous bile tract disease
- Chronic inflammatory states
V. Causes: False Negative
- False Negatives in 10% of population that fails to synthesize CA 19-9
VI. Efficacy: Pancreatic Ductal Adenocarcinoma Diagnosis
- CA 19-9 Level >37 U/ml
- Test Sensitivity: 72% (some studies have shown test sensitivities as low as 50%)
- Test Specificity: 86%
- Negative Likelihood Ratio (LR-): 0.32
- Positive Likelihood Ratio (LR+): 5.1
- High False Positive Rate in asymptomatic patients (do not use for screening)