Substance P: correlation of CSF and plasma levels
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J W Clark1, P D Senanayake, G D Solomon
1Cleveland Clinic Foundation, OH 44195-5039.
Objective:
To determine the correlation between cerebrospinal fluid and plasma concentrations of substance P.
Patients:
37 patients undergoing lumbar puncture for various diagnostic purposes.
Measurements:
Samples of cerebrospinal fluid and blood were obtained at the same visit. Substance P was measured by radioimmunoassay technique. At least 4 separate measurements were conducted on each sample to insure accuracy.
Results:
The mean plasma SP level was 1.195 (+/- 1.1). The mean cerebrospinal fluid substance P level was 1.075 (+/- .07). There was a statistically significant positive correlation between substance P level in the plasma and cerebrospinal fluid. The Pearson correlation coefficient was 0.656 (P < .0001) and the Spearman correlation coefficient was 0.698 (P < .0001).
Conclusions:
Plasma substance P levels closely correlate with cerebrospinal fluid substance P levels. This will simplify the measurement of substance P in the evaluation of therapeutic agents for headache.