The Doppler resistivity index of arteries near upper-trapezius sites does not differ between active trigger-point, latent trigger-point and palpably normal sites.

Ballyns 2011: resistivity index did not differ between active, latent and normal sites

what the source states

The source states that "No differences in RI values were detected between normal", latent and active sites, and that "the PI was not a good classifier of active, latent, or normal sites because of the large variance."

what we infer

A negative result recorded in its own right: one of the two Doppler indices shows no difference, and the other does not classify sites. The vascular signature at trigger points is partial, not categorical.

limitations

• Within-patient comparison in symptomatic subjects; the authors attribute the similarity partly to proximity of normal sites to trigger points.