Diagnostic accuracy of serum CA 19‑9 levels for malignancy in obstructive jaundice using histopathology as the reference standard: a cross-sectional study

Abstract

Introduction: Obstructive jaundice is a common presentation caused by benign and malignant hepatobiliary or pancreatic disease. Serum carbohydrate antigen 19-9 (CA 19-9) is frequently raised in malignant obstruction but can also rise with cholestasis and inflammation, which may limit diagnostic specificity. We assessed the diagnostic accuracy of serum CA 19-9 for malignancy in obstructive jaundice using histopathology as the reference standard.

Methods: We conducted a cross-sectional validation study over one year in the Department of General Surgery, Benazir Bhutto Hospital, Rawalpindi. Consecutive patients aged 15 to 65 years with obstructive jaundice, defined biochemically and clinically, were enrolled. Serum CA19-9 was measured by radioimmunoassay in a single private laboratory. A threshold of ≥200 IU/mL defined a positive index test. Endoscopic Retrograde Cholangio Pancreatography with brush cytology provided specimens for histopathology, which served as the reference standard. Sensitivity, specificity, positive predictive value, negative predictive value, and overall diagnostic accuracy were calculated from two-by-two tables with age stratified analyses.

Results: Two hundred and thirty two patients were included. The mean age was 51.9 ± 10.8 years and mean symptom duration was 15.5 ± 7.7 days. There were 144 men (62.07%) and 88 women (37.93%). Using the prespecified threshold, CA 19-9 indicated suspected malignancy in 123 patients (53.02%), while histopathology confirmed malignancy in 95 (40.95%). Overall sensitivity was 87.4%, specificity 70.8%, positive predictive value 67.5%, negative predictive value 89.0%, and diagnostic accuracy 77.6%. In patients aged 15 to 56 years, sensitivity was 93.9% and specificity 56.5%; in those aged 57 to 65 years, sensitivity was 80.4% and specificity 85.3%.

Discussion: Serum CA 19-9 at a threshold of ≥200 IU/mL provides supportive evidence for malignancy in obstructive jaundice but lacks specificity as a stand-alone discriminator. Interpretation should be integrated with clinical assessment, biochemistry, imaging, and tissue diagnosis, and consideration given to reassessment after biliary decompression.