• Takashi Fujiwara, Hiroshi Okamoto, Yasuhiro Ohnishi, Toshio Fukuoka, and Kazuyuki Ichimaru.
• Department of Otolaryngology Head and Neck Surgery, Ehime University, Toon City, Ehime, Japan.
• Emerg Med J. 2015 May 1;32(5):348-52.

ObjectiveTo assess the diagnostic accuracy of lateral neck radiographs (LNR) for acute supraglottitis in adults.DesignA single centre prospective observational study.SettingEmergency department at Kurashiki Central Hospital, Japan.ParticipantsAdult patients who underwent LNR to detect supraglottitis.Main Outcome MeasuresPresence of supraglottitis, based on nasopharyngeal laryngoscopy or a follow-up telephone call, 7-30 days after the visit.Results140 patients had LNR during the study period. 35 patients were excluded from further analysis because of lack of consent. Of the 105 eligible patients, 21 patients (20%) were given the diagnosis of supraglottitis: 17 of 29 with a radiographic abnormality, and 4 of 76 patients without a radiographic abnormality. Three of the four cases where LNR was negative was grade 1, and all cases of grade 3 or higher had abnormal LNR. Sensitivity and specificity (95% CI) of LNR for supraglottitis were 81.0% (64.2 to 97.7) and 85.7% (78.2 to 93.2), respectively. The positive predictive value of LNR was 58.6% (40.7 to 76.5) and the negative predictive value was 94.7% (89.7 to 99.8). The positive likelihood ratio of LNR was 5.67 (3.27 to 9.82) and the negative likelihood ratio was 0.22 (0.10 to 0.51).ConclusionsLNR showed only moderate sensitivity and specificity for supraglottitis and would miss some cases of supraglottitis if the pre-test probability is high. LNR was very sensitive for grade 3 or higher supraglottitis, but would miss milder cases.Trial RegistrationUMIN000011928.Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

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