NeuroQuick--a novel bedside test for small fiber neuropathy?

BACKGROUND: An appropriate bedside test for small fiber neuropathy does not exist so far. Cold hypaesthesia occurs as an early onset symptom, and the new handheld device NeuroQuick (NQ) was recently claimed to be a valid and reliable screening tool for its quantitative assessment.

AIMS: Comparison of the NQ with standardized quantitative sensory testing (QST) in patients suffering from chronic painful dysaesthesia with and without pathological cold detection threshold (CDT).

METHODS: Forty-one patients with and without diabetes mellitus displaying chronic painful dysaesthesia were included (18 men, 55.8+/-13 years). According to the German network protocol QST was performed in the body area with the severest symptoms and at the opposite side as control after thorough clinical-neurological examination. The NeuroQuick, developed as quantitative bedside testing of cold thermal perception based on the wind chill, was used subsequently.

RESULTS: DT was pathologically increased in 14 and within normal range in 27 patients; NQ values were pathological in 9 and non-pathological in 32 patients. Thus NQ obtained 7.4% false positive and 50% false negative results in detecting cold hypaesthesia, corresponding to 92.6% specificity, 50% sensitivity and a positive and negative predictive value of 78%, respectively.

CONCLUSIONS: This study demonstrates that the NeuroQuick is not an adequate screening device for cold hypaesthesia in patients with chronic neuropathic pain. It exhibits a high specificity but only low sensitivity in the identification of such small fiber dysfunction; a reliable and valid screening tool should necessarily provide opposite features.