Translation and Validation of the Hindi Version of Neuropathic Pain Symptom Inventory: A Prospective Cohort Study

Neuropathic pain (NP) is caused by a lesion or disease of the somatosensory nervous system, and its timely prediction is important for its management. NP symptom inventory (NPSI) has been reported to have a high test-retest reliability, sensitivity and specificity along with a good construct validity. It has been translated and validated into several languages except Hindi. Hence, the present study aimed to validate the Hindi Version of the NPSI (NPSI-H) for the identification and assessment of NP. We translated the English version of the NPSI questionnaire into Hindi first and planned the study with the primary objective to assess the reliability and validity of the NPSI-H. The secondary objectives were to assess the correlation between the NPSI total (NPSI[T]) score, optimal cutoff for NPSI based on Douleur Neuropathique 4 questionnaire (DN-4) and numeric rating scale (NRS)-pain with sensitivity and specificity.

After Institutional Ethics Committee (IEC) approval and prospective Clinical Trials Registry - India (CTRI) registration, this prospective observational study was conducted in patients with post-herpetic neuralgia (PHN) with evident hyperalgesia and allodynia confined to midthoracic and lower thoracic dermatomes for at least 12 weeks after the healing of rash with visual analogue scale-pain ≥4. The NPSI-H questionnaire was filled twice over an interval of 1 h by two different raters as self-reported responses at both baseline and at 4 weeks. The NRS-pain and quality of life (QoL) using the short form-12 questionnaire were recorded only twice, once at baseline and then at the 4^th week. However, DN-4 was recorded only once, that is, at baseline. A previous study validating the Hindi version of the DN-4 pain questionnaire was used for sample size calculation. Cronbach's alpha coefficient was calculated for the NPSI(T) score and also after removing each of the items for both raters. To assess the validity, the Spearman correlation was used to NRS-pain score and NPSI(T) at different time intervals. The receiver operative characteristic curve was applied to find the discriminant validity of NPSI, considering the NRS-pain ≥5 and the DN-4 score ≥4 as poor.

This study involved 230 patients with PHN. The Cronbach's alpha coefficient was >0.8 for NPSI(T) for each item at both time intervals by both raters. A significant correlation was observed between the NRS-pain score, DN-4 and NPSI(T) score at both designated time points by both raters, indicating excellent convergent validity. A moderate negative correlation was observed between the NPSI(T) score and QoL-P at both time points. The optimal NPSI cutoffs at baseline with NRS-pain were>35.76, and considering the NRS-Pain ≥5 as poor, at this point, sensitivity was 83.11%, and specificity was 100% indicating an excellent discriminant power of NPSI-H. Similarly, the optimal cutoff point of NPSI with DN-4 score ≥4 was 35.7 at baseline; sensitivity and specificity at this point were 76.3% and 100/%, respectively.

We observed that the present study's results indicate that the NPSI-H questionnaire has excellent essential psychometric properties, including reliability, feasibility and validity.