How to Critically Appraise A Diagnostic Article Sandy De Groote

Clinical Situation 4 A doctor comes to you. She has a 21 year old male patient she suspects has an ulcer and wants to do a test for H. pylori infection. She has heard of a new stool antigen test that she hopes will be less invasive and less expensive than other tests. The doctor wants to know more about this test.

PICO 4 P: Young adult with possible H Pylori 4 I: How accurate is stool antigen test 4 C: In comparison with other tests 4 O: Diagnosis H. Pylori Infection

Search 4 PubMed Clinical Queries (diagnosis, specificity) –Helicobacter pylori AND stool antigen AND non-invasive

The Article Selected 4 Diagnosis of Helicobacter Pylori infection with a new non-invasive antigen-based assay Lancet 1999; 354:30-33

Methods 4 Design: Prospective 4 Setting: Multicentre study (11) in Europe 4 Patients: 501 (276 male, 255 women); Age range years; Undergoing gastroscopy at endoscopy 4 Description of diagnostic tests: Presence of H. Pylori was invasively confirmed if histology (antrum, corpus, or both) and urease test were positive, or if culture was positive. (Gold Standard – proven method) 4 Presence of H. Pylori was non-invasively confirmed if antigens were found in stool samples using the HpSA (Meridian Diagnostics) (new diagnostic test) 4 Patients classified as having H Pylori infection received an eradication regimen; 107 were reassessed 4 weeks after therapy

Issues of Validity 4 Was there an independent, blind comparison with a reference (“gold”) standard of diagnosis? – Yes 4 Was the diagnostic test evaluated in an appropriate spectrum of patients? Yes 4 Was the reference standard applied regardless of the diagnostic test result? Yes

Results 4 Look at results in paper –-examined urea breath test –Stool antigen test (what we will examine) –Table 1 (pg 31) 4 Use 2X2 Diagnostic Test Calculator found at ebm.peds.uic.edu 4 Crunch in the numbers – various approaches

Applicability 4 Stool antigen tests could be used reliably to diagnosis H.pylori