ABSTRACT
When searching the medical care literature for evidence on a diagnostic test, three
questions should be addressed each time a study is found: (1) Is this evidence about
a diagnostic test valid? (2) Does the test accurately discriminate between patients
who do and patients who do not have a specific disorder? (3) Can the test be applied
to this patient who is right now sitting in front of me? We will discuss hysterosalpingography
(HSG) as an example of a valid and accurate diagnostic test to be applied in a general population of subfertile couples to assess tubal
patency (specificity 0.83). HSG is an unreliable test for diagnosing tubal occlusion
however (sensitivity 0.65). If HSG were normal, other investigations could be pursued
and diagnostic laparoscopy (LS) only performed if conception had not occurred by a
later date. If HSG were abnormal, LS would be needed to confirm or exclude tubal occlusion.
Patients with risk factors for pelvic or tubal disease, including an abnormal Chlamydia
antibody test (CAT) and those showing abnormalities at pelvic examination, should
proceed directly to LS because they are significantly more likely to have pelvic pathology.
A completely different issue would be HSG as a prognostic test for the occurrence of pregnancy. In theory, the occurrence of pregnancy may
be considered a gold standard; however, in reproductive medicine, with so many causes
of subfertility other than tubal pathology, a diagnostic test for one single disorder,
if normal, will never be able to accurately predict the eventual occurrence of pregnancy.
KEYWORDS
Hysterosalpingography - laparoscopy - PICO - Chlamydia antibody testing - tubal factor
subfertility
