Clinical decision rule for decreasing unnecessary CT / LP to evaluate for subarachnoid hemorrhage (SAH) in patients with headaches who have none of the following.

Inclusion criteria:

Exclusion criteria:

Sensitivity: 100% (n=1826, 132 SAH)
Specificity: 15%
NPV: 100%
(-) LR: 0.024

Perry JJ et al. Clinical Decision Rules to Rule Out Subarachnoid Hemorrhage for Acute Headache. JAMA. 2013; 310(12): 1248-1255.