Reliability and Validity of Punctuate Pain Thresholds and Self-Reported Pain

Methods: 30 healthy female subjects without orofacial pain were tested in two sessions 1–2­ weeks apart. Test site was the mucobuccal fold adjacent to the first upper right premolar. Active (lidocaine hydrochloride 2%; Dynexan®) or placebo gel was applied for 5 minutes, and sensory testing was performed before and after application. The standardized QST protocol included mechanical pain threshold (MPT; g) pressure pain threshold (PPT; kPa), mechanical pain stimulus (MPS; 0–100 NRS) and needle penetration stimulus (NPS; 0–100 NRS). An electronic von Frey device (EvF, Somedic®, Hörby, Sweden) delivered all stimuli. Intraclass correlation coefficient (ICC) calculated the test-retest reliability for all variables within sessions. Student´s t-test determined differences in anesthetic effect between pharmacological agents.  Pearson’s correlation coefficient (r) analyzed convergent validity by comparing sharp/dull sensations during NPS and MPS stimuli, and divergent validity by comparing NPS and PPT stimuli.

Results: 29 female subjects, mean age 29.0±10.2 years completed the study. No significant difference was found between active and placebo gel for any of the measures. Test-retest reliability at 10-minute intervals between examinations was 0.69 for MPT, 0.79 for PPT, 0.72 for MPS, and 0.86 for NPS. A high correlation was found between NPS and MPS r = 0.84 (p < 0.001), and a low correlation for NPS and PPT r = -0.22 (p = 0.25).

Conclusion: The study found good to excellent test-retest reliability for all measures. None of the measures was sensitive enough to detect differences in anesthetic effect between active and placebo gel. MPT/MPS measurements with an EvF device have good validity.