PubMed · 9646959
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L A Boardman, J F Peipert. 1998. Screening and diagnostic testing.. https://doi.org/10.1097/00003081-199806000-00007
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The interest in studying gene-environment interaction is increasing for complex diseases. However, most methods of detecting gene-environment interactions may not be appropriate for the study of interactions involving rare genes (G:) or uncommon environmental exposures (E:), because of poor statistical power. To increase this power, the authors propose the counter-matching design. This design increases the number of subjects with the rare factor without increasing the number of measurements that must be performed. In this paper, the efficiency and feasibility (required sample sizes) of counter-matching designs are evaluated and discussed. Counter-matching on both G: and E: appears to be the most efficient design for detecting gene-environment interaction. The sensitivity and specificity of the surrogate measures, the frequencies of G: and E:, and, to a lesser extent, the value of the interaction effect are the most important parameters for determining efficiency. Feasibility is also more dependent on the exposure frequencies and the interaction effect than on the main effects of G: and E: Although the efficiency of counter-matching is greatest when the risk factors are very rare, the study of such rare factors is not realistic unless one is interested in very strong interaction effects. Nevertheless, counter-matching appears to be more appropriate than most traditional epidemiologic methods for the study of interactions involving rare factors.
HYPOTHESIS: In good-risk patients with variceal bleeding undergoing portal decompression, surgical shunt is more effective, more durable, and less costly than angiographic shunt (transjugular intrahepatic portasystemic shunt [TIPS]). DESIGN: Retrospective case-control study. SETTING: Academic referral center for liver disease. PATIENTS: Patients with Child-Pugh class A or B cirrhosis with at least 1 prior episode of bleeding from portal hypertension (gastroesophageal varices, portal hypertensive gastropathy). INTERVENTION: Portal decompression by angiographic (TIPS) or surgical (portacaval, distal splenorenal) shunt. MAIN OUTCOME MEASURES: Thirty-day and long-term mortality, postintervention diagnostic procedures (endoscopic, ultrasonographic, and angiographic studies), hospital readmissions, variceal rebleeding episodes, blood transfusions, shunt revisions, and hospital and professional charges. RESULTS: Patients with Child-Pugh class A or B cirrhosis undergoing TIPS (n = 20) or surgical shunt (n = 20) were followed up for 385 and 456 patient-months, respectively. Thirty-day mortality was greater following TIPS compared with surgical shunt (20% vs 0%; P =.20); long-term mortality did not differ. Significantly more rebleeding episodes (P<.001); rehospitalizations (P<.05); diagnostic studies of all types (P<.001); shunt revisions (P<.001); and hospital (P<.005), professional (P<.05), and total (P<. 005) charges occurred following TIPS compared with surgical shunt. CONCLUSIONS: Operative portal decompression is more effective, more durable, and less costly than TIPS in Child-Pugh class A and B cirrhotic patients with variceal bleeding. Good-risk patients with portal hypertensive bleeding should be referred for surgical shunt.