Comparison of the number of included studies investigating a given biomarker modality with the number reporting a significant association between the biomarker modality and a clinical measure of disease progression.

Two studies examined for a relationship between two different biomarker modalities (MRI and MRS in one study; MRI and CSF in another study) and a clinical measure of disease progression. (MRI, magnetic resonance imaging; CSF, cerebrospinal fluid; MRS, magnetic resonance spectroscopy; PET, positron emission tomography; SPECT, single-photon emission computed tomography; CT, computed tomography).