Symptom association probability and symptom sensitivity index: preferable but still suboptimal predictors of response to high dose omeprazole

• Published in: Gut Vol. 54; no. 8; pp. 1067 - 1071
• Main Authors: Taghavi, S A, Ghasedi, M, Saberi-Firoozi, M, Alizadeh-Naeeni, M, Bagheri-Lankarani, K, Kaviani, M J, Hamidpour, L
• Format: Journal Article
• Language: English
• Published: London BMJ Publishing Group Ltd and British Society of Gastroenterology 01.08.2005; BMJ; BMJ Publishing Group LTD; Copyright 2005 by Gut
• Subjects: Acids; Adult; Biological and medical sciences; Decision theory; Diagnostic tests; Drug Administration Schedule; Endoscopy; Esophagus; Female; gastro-oesophageal reflux; gastro-oesophageal reflux disease; Gastroenterology; Gastroenterology. Liver. Pancreas. Abdomen; Gastroesophageal reflux; Gastroesophageal Reflux - complications; Gastroesophageal Reflux - diagnosis; Gastroesophageal Reflux - drug therapy; GOR; GORD; heartburn; Heartburn - diagnosis; Heartburn - drug therapy; Heartburn - etiology; Humans; Hydrogen-Ion Concentration; Investigations; Male; Medical sciences; Middle Aged; Monitoring, Ambulatory - methods; Oesophagus; Omeprazole; Omeprazole - administration & dosage; omeprazole test; Other diseases. Semiology; Pain; pH effects; Pharmaceutical industry; PPI; Prospective Studies; proton pump inhibitor; Proton Pump Inhibitors; receiver operating characteristic; ROC; ROC Curve; SAP; Sensitivity and Specificity; SSI; Statistical analysis; symptom association probability; symptom index; symptom sensitivity index; Gastroesophageal reflux; Enzyme; Esophageal disease; H; Enzyme inhibitor; Antiulcer agent; K; Proton pump inhibitor; Omeprazole; Symptomatology; Sensitivity; Benzimidazole derivatives; Antisecretory agent; Gastroenterology; Digestive diseases; exchanging ATPase; Hydrolases; Predictive factor; High dose
• ISSN: 0017-5749; 1468-3288; 1458-3288
• DOI: 10.1136/gut.2004.054981

Background: Twenty four hour oesophageal pH monitoring is frequently used to quantify the association between a patient’s symptom and gastro-oesophageal reflux. Three indices (symptom association probability (SAP), symptom index (SI), and symptom sensitivity index (SSI)) are used to quantify and establish this relation. Aims: The aim of the present study was to compare these indices against the omeprazole test (OT) as an objective indicator of reflux induced symptoms. Methods: Fifty two patients with a predominant symptom of heartburn were enrolled from gastroenterology and primary care clinics. Baseline symptom score was calculated at the fist visit. All patients underwent 24 hour oesophageal pH monitoring, and symptom-reflux association indices were calculated. All patients were placed on high dose omeprazole (40 mg in the morning, 20 mg at night) after completion of pH monitoring and symptom score was recorded again after one week. Results: Thirty eight patients completed the study. All three indices were significantly related to each other (p<0.001). SAP and SSI (with a new cut off of 1.3, but not with the commonly used 5%) had statistically significant relations with OT (p<0.05 for both). SSI had the highest positive and negative predictive values and sensitivity. The specificity of SSI and SAP was equal and lower than SI. Areas under the receiver operating characteristic (ROC) curve for the three indices were not significantly different from each other or from a hypothetical non-discriminating test. Per cent time pH <4, sex, and age had no relation to OT and no effect on its correlation with association indices. No cut off point could be found at which the results of SI could be related significantly to the OT results. Conclusion: SAP and SSI are significantly related to symptomatic response to high dose omeprazole; however, they are far from perfect, with a significant number of discordant cases as well as relatively small areas under the ROC curves. We suggest that the new cut off of 1.3 be used for SSI in the future. Further research is needed to identify possible methods to improve the discrimination power of these indices or to identify possible patient characteristics that may affect this relation.