Thirty studies that reported results for 34 independent patient series were included in the review; sample size ranged from 51 to 532. Most studies used a diagnostic case-control design. Other quality criteria which were poorly rated (met by 10 or less studies) were histological confirmation of all exocrine pancreatic cancer cases, blinded interpretation of K-ras results, and explanation for exclusion of participants from K-ras analysis.
The pooled sensitivity estimates for K-ras determination were poor in serum or plasma samples (37.6%; 95% CI 17.5 to 63.1%; four studies), stool samples (65.7%; 95% CI 38.2 to 85.5%; three studies) and pancreatic juice (60.0%; 95% CI 43.6 to 74.5%; nine studies). The pooled sensitivity estimates for K-ras determination in tissue samples were 76.5% (95% CI 66.7 to 84.2%) and specificity estimates were 91.8% (95% CI 87.6 to 94.7); 17 studies.
Sensitivity was significantly higher in studies that used a case-control design than in those that used more clinically relevant patient groups (82.7% compared with 68.4%, P = 0.039). Studies that determined K-ras in all patients reported higher sensitivity than studies that excluded some patients (83.8% compared with 66.3%, P = 0.004). for the five studies that reported data by tumour stage, sensitivity in stage IV tumours was greater than in stages I to III; the pooled estimate was 30.5% (95% CI 19.5 to 44.0%) for tumours in stages I to III and 71.6% (95% CI 61.6 to 79.8%) for stage IV tumours.
Eight studies reported data for the combination of K-ras mutations with cytopathology; sensitivities ranged from 53.3% (95% CI 27.4 to 77.7%) to 97.0% (95% CI 82.5 to 99.8%) and specificities ranged from 61.5% (95% CI 32.3 to 84.9%) to 100% (95% CI 82.8 to 100%)