Perfect diagnostic tests do not exist. No test detects all cases of the diagnosis sought while excluding the diagnosis in all patients not having the condition in question.
All tests sometimes give both false positive and false negative results.
Criteria have been published that clinicians can use to determine when a diagnostic test is useful. Its rational use depends on how well it meets these standards. NAI can be used to diagnose serious causes of low back pain, such as cauda equina syndrome or malignant disease. Serious causes of low back pain are extremely rare in the population cared for by primary care providers. Therefore, very few patients will need NAI to look for serious causes of acute low back pain.