Diagnostic usefulness of Carnett's test in psychogenic abdominal pain

Carnett's test is a simple clinical test in which abdominal tenderness is evaluated while the patient tenses the abdominal muscles. It is useful for differentiating abdominal wall pain from intra-abdominal pain. However, no study has reported its association with psychogenic abdominal pain. We evaluated its diagnostic usefulness in psychogenic abdominal pain.

Two physicians performed Carnett's test on each patient, but only one received the medical history. The other physician only conducted the test. Based on the final diagnosis, patients were categorized into 3 groups: psychogenic pain, abdominal wall pain, or intra-abdominal pain. Each group was analyzed in association with the results of Carnett's test conducted by the blinded physician.

A total of 130 outpatients with the chief complaint of abdominal pain who had abdominal tenderness.

There were 22 patients with psychogenic abdominal pain, 19 with abdominal wall pain and 62 with intra-abdominal pain. In patients with psychogenic pain or abdominal wall pain, Carnett's test was usually positive, whereas the test was usually negative in patients with intra-abdominal pain (p<0.001, respectively). The positive likelihood ratio of Carnett's test for psychogenic abdominal pain was 2.91 (95% confidence interval [CI], 2.71-3.13), while the negative likelihood ratio was 0.19 (95% CI, 0.11-0.34). The corresponding values for abdominal wall pain were 2.62 (95% CI, 2.45-2.81) and 0.23 (95% CI, 0.13-0.41), respectively.

Carnett's test may be useful for ruling in and ruling out psychogenic abdominal pain in addition to distinguishing between abdominal wall pain and intra-abdominal pain.