Nosographic analysis of osmophobia and field testing of diagnostic criteria including osmophobia

Osmophobia has been suggested as an additional symptom of migraine without aura, and a high prevalence of osmophobia of up to 50% has been reported in the literature. We conducted a nosographic study of osmophobia in all migraineurs and tension-type headache patients and a field testing of suggested diagnostic criteria of osmophobia, presented in the appendix of the second edition of The International Classification of Headache Disorders and suggested by Silva-Néto et al. and Wang et al ., in migraine without aura and tension-type headache patients (n = 1934).

Each patient received a validated semi-structured interview. All subjects fulfilled the diagnostic criteria of the second edition of The International Classification of Headache Disorders for migraine or tension-type headache. Statistical analyses were performed using statistical software R. The statistical R package "Caret" was used to construct a confusion matrix and retrieve sensitivity, which is defined as the suggested criteria's ability to correctly diagnose migraine without aura patients, and specificity, defined as the suggested criteria's ability to not wrongly diagnose tension-type headache patients.

Osmophobia was present in 33.5% of patients with migraine with aura, in 36.0% of patients with migraine without aura, and in 1.2% of patients with tension-type headache. All migraineurs with osmophobia also fulfilled the current criteria for migraine by having nausea or photophobia and phonophobia. The appendix criteria had a sensitivity of 0.96 and a specificity of 0.99 for migraine without aura, and a sensitivity of 0.65 and a specificity of 0.99 for probable migraine without aura. Both the criteria by Silva-Néto et al. and Wang et al. had a sensitivity of 0.98 and a specificity of 0.99 for migraine without aura, and a sensitivity of 0.66 and a specificity of 0.99 for probable migraine without aura.

This study demonstrates the remarkable specificity of osmophobia. The criteria by Silva-Néto et al. and Wang et al. both had a higher sensitivity than the appendix criteria for migraine without aura; all three criteria had a low sensitivity for probable migraine without aura. However, neither the appendix criteria nor the criteria by Silva-Néto et al. or Wang et al. added any extra patients that would not have been diagnosed by the current diagnostic criteria for migraine. Osmophobia is a valuable symptom that may be useful to differentiate between migraine without aura and tension-type headache in difficult clinical cases.

Our results do not suggest that alterations of the current diagnostic criteria for migraine without aura are needed.