Correspondence / American Journal of Emergency Medicine 32 (2014) 1278–1293
Target population in pulmonary embolism rule-out criteria studies—the authors reply To the Editor, We agree that the pulmonary embolism rule-out criteria (PERC) should be applied only to clinical scenarios with a low pretest probability (PTP), where it has been previously validated. We also agree that out study design has some limitations, namely, you mentioned that we did not include all patients suspected of having pulmonary embolism (PE; ie, those whom had D-dimer testing completed that was negative precluding further testing) [1]. As mentioned, including these patients would have resulted in a negative predictive value (NPV) for PERC closer to the results extrapolated from your study, mentioned in the correspondence (NPV, 99.8%; 95% confidence interval, 98.7%-100%) [2]. Because we did not include all “low-risk” patients in our study, we came to the similar conclusion that the NPV would have been higher, with a narrower confidence interval, further strengthening the argument that PERC may be used safely when PTP is low for PE. We also agree that the one case of PE in our sample of 83 patients whom were PERC negative may have had a moderate to high PTP for PE, precluding use of PERC in the evaluation for PE. As mentioned by Kline et al in the original derivation of PERC, there are numerous clinical factors not included in the rule that may lead to further testing in any given patient (ie, morbidly obese patients, strong family history of thrombosis, concurrent β-blocker use, patients with amputations, etc.) [3]. Thus, physicians must impose clinical judgment for patients with borderline or indeterminate clinical variables, as there is no one simple nomogram available for safe use in every clinical scenario. Andrew L. Bozarth, MD Navin Bajaj, MD Margaret R. Wessling, MD Dustin Keffer, DO Shais Jallu, MD Gary A. Salzman, MD University of Missouri-Kansas City School of Medicine Kansas City, MO E-mail address: [email protected] http://dx.doi.org/10.1016/j.ajem.2014.07.005 References [1] Bozarth AL, Bajaj N, Wessling MR, Keffer D, Jallu S, Salzman GA. Evaluation of the Pulmonary Embolism Rule-Out Criteria in a Retrospective Cohort at an Urban Academic Hospital. Am J Emerg Med 2014;0(0). http://dx.doi.org/10.1016/j.ajem. 2013.10.010 [Epub ahead of print]. [2] Bokobza J, Aubry A, Nakle N, Vincent-Cassy C, Pateron D, Devilliers C, et al. Pulmonary embolism rule-out criteria vs D-dimer testing in low-risk patients for pulmonary embolism: a retrospective study. Am J Emerg Med 2014;32(6):609–13. http://dx.doi.org/10.1016/j.ajem.2014.03.008. [3] Kline JA, Mitchell AM, Kabrhel C, Richman PB, Courtney DM. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism. J Thromb Haemost 2004;2(8):1247–55.
tion [1]. It requires special equipment and personnel who are familiar with operating a laryngoscope; either of which is accessible 24 hours a day in most emergency departments (EDs). Therefore, patients suspected of acute supraglottitis are usually referred for diagnoses, which increase the chance of a futile referral and of disastrous airway obstruction during transportation. The utility of computed tomography (CT) scans in the diagnosis and management of supraglottitis is still debated. A study by Smith et al [2] described the appearance of supraglottitis on CT and suggested that CT may serve as a diagnostic tool when a laryngoscopic examination is unavailable. Another prospective study conducted in South Korea proposed that CT should be performed in all patients with supraglottitis for early diagnosis of epiglottic abscesses [3]. Accordingly, we conducted this retrospective study to verify the usefulness and limitation of CT in the diagnosis and management of supraglottitis. We reviewed all ED patients who were suspected of having supraglottitis and underwent laryngoscopy to confirm the diagnosis from February 2010 to July 2012. Among the 291 reviewed patients, 40 cases underwent CT in the ED. Of the patients who underwent CT, 17 were diagnosed with supraglottitis, and 23 patients were not. Positive results on CT were defined as thickening of the epiglottis, aryepiglottic folds, vocal cords, muscle, and subcutaneous fat and obliteration of the pre-epiglottic fat [1,2]. Positive results for neck x-rays were defined as official radiographic reports that indicated any suspicion of supraglottitis. Eleven supraglottitis cases had positive CT results, and 6 supraglottitis cases had negative CT results. All 23 patients without supraglottitis had negative CT results. The CT diagnostic characteristics for supraglottitis were as follows: 65% sensitivity, 100% specificity, 100% positive predictive value, and 79% negative predictive value. On neck x-ray, 10 patients with supraglottitis and 5 patients without supraglottitis had positive results, and 7 patients with supraglottitis and 17 patients without supraglottitis had negative results. The neck x-ray was omitted for 1 patient without supraglottitis. The neck x-ray diagnostic characteristics for supraglottitis were as follows: 59% sensitivity, 74% specificity, 67% positive predictive value, and 71% negative predictive value. The CT findings for all patients are presented in the Table. In patients with supraglottitis with negative CT results, the CT indicated deep neck space infections in 2 cases, head and neck carcinomas in 2 cases, swelling of the hypopharyngeal wall in 1 case, and swelling of the tongue base in 1 case. Two patients with supraglottitis underwent a surgical intervention, one for supraglottitis complicated by deep neck space infection and the other for an epiglottic foreign body and abscess. The most common CT findings in patients without supraglottitis were tonsillitis/peritonsillar abscesses and deep neck space infections. Other discoveries on CT included 1 sialadenitis, 1 jugular foramen tumor causing vocal cord palsy, 3 thoracic abnormalities (pneumonia, pulmonary embolism, and thoracic goiter), and 1 negative result.
Table The CT findings of patients with and without supraglottitis Patients without supraglottitis (23) All negative results of CT
Computed tomography scan as a diagnostic tool for supraglottitis in adults
To the Editor, The diagnostic criterion standard for supraglottitis is direct visualization of the supraglottic area during laryngoscopic examina-
1279
Supraglottitis (11) Positive results of CT Supraglottitis (6) Negative results of CT
Tonsillitis/peritonsillar abscess Deep neck space infection Sialadenitis Jugular foramen tumor Pneumonia Pulmonary embolism Thoracic goiter negative Supraglottitis Epiglottic foreign body and abscess Deep neck space infection Thyroid cancer Nasopharyngeal cancer Swelling of hypopharyngeal wall Swelling of tongue base
12 5 1 1 1 1 1 1 10 1 2 1 1 1 1
Target population in pulmonary embolism rule-out criteria studies—the authors reply To the Editor, We agree that the pulmonary embolism rule-out criteria (PERC) should be applied only to clinical scenarios with a low pretest probability (PTP), where it has been previously validated. We also agree that out study design has some limitations, namely, you mentioned that we did not include all patients suspected of having pulmonary embolism (PE; ie, those whom had D-dimer testing completed that was negative precluding further testing) [1]. As mentioned, including these patients would have resulted in a negative predictive value (NPV) for PERC closer to the results extrapolated from your study, mentioned in the correspondence (NPV, 99.8%; 95% confidence interval, 98.7%-100%) [2]. Because we did not include all “low-risk” patients in our study, we came to the similar conclusion that the NPV would have been higher, with a narrower confidence interval, further strengthening the argument that PERC may be used safely when PTP is low for PE. We also agree that the one case of PE in our sample of 83 patients whom were PERC negative may have had a moderate to high PTP for PE, precluding use of PERC in the evaluation for PE. As mentioned by Kline et al in the original derivation of PERC, there are numerous clinical factors not included in the rule that may lead to further testing in any given patient (ie, morbidly obese patients, strong family history of thrombosis, concurrent β-blocker use, patients with amputations, etc.) [3]. Thus, physicians must impose clinical judgment for patients with borderline or indeterminate clinical variables, as there is no one simple nomogram available for safe use in every clinical scenario. Andrew L. Bozarth, MD Navin Bajaj, MD Margaret R. Wessling, MD Dustin Keffer, DO Shais Jallu, MD Gary A. Salzman, MD University of Missouri-Kansas City School of Medicine Kansas City, MO E-mail address: [email protected] http://dx.doi.org/10.1016/j.ajem.2014.07.005 References [1] Bozarth AL, Bajaj N, Wessling MR, Keffer D, Jallu S, Salzman GA. Evaluation of the Pulmonary Embolism Rule-Out Criteria in a Retrospective Cohort at an Urban Academic Hospital. Am J Emerg Med 2014;0(0). http://dx.doi.org/10.1016/j.ajem. 2013.10.010 [Epub ahead of print]. [2] Bokobza J, Aubry A, Nakle N, Vincent-Cassy C, Pateron D, Devilliers C, et al. Pulmonary embolism rule-out criteria vs D-dimer testing in low-risk patients for pulmonary embolism: a retrospective study. Am J Emerg Med 2014;32(6):609–13. http://dx.doi.org/10.1016/j.ajem.2014.03.008. [3] Kline JA, Mitchell AM, Kabrhel C, Richman PB, Courtney DM. Clinical criteria to prevent unnecessary diagnostic testing in emergency department patients with suspected pulmonary embolism. J Thromb Haemost 2004;2(8):1247–55.
tion [1]. It requires special equipment and personnel who are familiar with operating a laryngoscope; either of which is accessible 24 hours a day in most emergency departments (EDs). Therefore, patients suspected of acute supraglottitis are usually referred for diagnoses, which increase the chance of a futile referral and of disastrous airway obstruction during transportation. The utility of computed tomography (CT) scans in the diagnosis and management of supraglottitis is still debated. A study by Smith et al [2] described the appearance of supraglottitis on CT and suggested that CT may serve as a diagnostic tool when a laryngoscopic examination is unavailable. Another prospective study conducted in South Korea proposed that CT should be performed in all patients with supraglottitis for early diagnosis of epiglottic abscesses [3]. Accordingly, we conducted this retrospective study to verify the usefulness and limitation of CT in the diagnosis and management of supraglottitis. We reviewed all ED patients who were suspected of having supraglottitis and underwent laryngoscopy to confirm the diagnosis from February 2010 to July 2012. Among the 291 reviewed patients, 40 cases underwent CT in the ED. Of the patients who underwent CT, 17 were diagnosed with supraglottitis, and 23 patients were not. Positive results on CT were defined as thickening of the epiglottis, aryepiglottic folds, vocal cords, muscle, and subcutaneous fat and obliteration of the pre-epiglottic fat [1,2]. Positive results for neck x-rays were defined as official radiographic reports that indicated any suspicion of supraglottitis. Eleven supraglottitis cases had positive CT results, and 6 supraglottitis cases had negative CT results. All 23 patients without supraglottitis had negative CT results. The CT diagnostic characteristics for supraglottitis were as follows: 65% sensitivity, 100% specificity, 100% positive predictive value, and 79% negative predictive value. On neck x-ray, 10 patients with supraglottitis and 5 patients without supraglottitis had positive results, and 7 patients with supraglottitis and 17 patients without supraglottitis had negative results. The neck x-ray was omitted for 1 patient without supraglottitis. The neck x-ray diagnostic characteristics for supraglottitis were as follows: 59% sensitivity, 74% specificity, 67% positive predictive value, and 71% negative predictive value. The CT findings for all patients are presented in the Table. In patients with supraglottitis with negative CT results, the CT indicated deep neck space infections in 2 cases, head and neck carcinomas in 2 cases, swelling of the hypopharyngeal wall in 1 case, and swelling of the tongue base in 1 case. Two patients with supraglottitis underwent a surgical intervention, one for supraglottitis complicated by deep neck space infection and the other for an epiglottic foreign body and abscess. The most common CT findings in patients without supraglottitis were tonsillitis/peritonsillar abscesses and deep neck space infections. Other discoveries on CT included 1 sialadenitis, 1 jugular foramen tumor causing vocal cord palsy, 3 thoracic abnormalities (pneumonia, pulmonary embolism, and thoracic goiter), and 1 negative result.
Table The CT findings of patients with and without supraglottitis Patients without supraglottitis (23) All negative results of CT
Computed tomography scan as a diagnostic tool for supraglottitis in adults
To the Editor, The diagnostic criterion standard for supraglottitis is direct visualization of the supraglottic area during laryngoscopic examina-
1279
Supraglottitis (11) Positive results of CT Supraglottitis (6) Negative results of CT
Tonsillitis/peritonsillar abscess Deep neck space infection Sialadenitis Jugular foramen tumor Pneumonia Pulmonary embolism Thoracic goiter negative Supraglottitis Epiglottic foreign body and abscess Deep neck space infection Thyroid cancer Nasopharyngeal cancer Swelling of hypopharyngeal wall Swelling of tongue base
12 5 1 1 1 1 1 1 10 1 2 1 1 1 1
