Table 2.
Selected studies evaluating diagnostic performance of US, from 1994 to 2009
| Reference | Study design | N | Sensitivity (%) | Specificity (%) |
|---|---|---|---|---|
| Balthazar et al [60], 1994 | Prospective. Consecutive patients, age 15–82 y, with “suggestive but not typical clinical and laboratory findings of appendicitis” evaluated by both CT and US. Clinical follow-up for nonsurgical patients. | 100 | 76 | 91 |
| Horton et al [25], 2000 | Prospective. Patients, age 18–65 y, with possible appendicitis but missing 1 or more classic clinical findings. Subjects randomized to CT or US. No description of follow-up protocol for nonsurgical patients. | 40 (US) | 76 | 90 |
| Dilley et al [27], 2001 | Retrospective review of all rule-out appendicitis US cross-referenced to surgical and pathology reports. Pediatric patients. Study includes repeat US. No description of follow-up protocol for nonsurgical patients. | 2056 | 89a 93b |
95a 95b |
| Lowe et al [89], 2001 | Retrospective. Consecutive children with suspected appendicitis underwent CT and compared with a historical cohort of consecutive children who underwent US. 12 children with negative imaging studies lost to follow-up and excluded. | 78 (US) | 100 | 88 |
| Rettenbacher et al [66], 2002 | Prospective. Patients, age 5–92 y, with suspected appendicitis. All underwent US. Clinical follow-up for nonsurgical patients. | 350 | 98c 97d |
98c 100d |
| Poortman et al [64], 2003 | Prospective. Adult and pediatric patients with suspected appendicitis. Subjects underwent both US and CT. For nonsurgical patients median follow-up was 13 mo. | 226 | 79 | 78 |
| Kessler et al [68], 2004 | Prospective. Patients, age 15–83 y, with suspected appendicitis. Follow-up in nonsurgical patients was chart review and telephone call at least 6 mo from discharge. Specific US findings were evaluated for diagnostic performance. Appendiceal diameter ≥6 mm was most sensitive and specific finding for appendicitis; sensitivity and specificity for this finding reported here. | 125 | 98 | 98 |
| Keyzer et al [62], 2005 | Prospective. Patients, age 16–81 y, referred for CT for suspected appendicitis; all patients underwent both CT and US. Follow-up obtained from medical record and telephone call at 1 mo. | 94 | 77 | 87 |
| Doria et al [61], 2006 | Meta-analysis (adults): study design described in text. | N/A | 83e | 93e |
| Doria et al [61], 2006 | Meta-analysis (children): study design described in text. | N/A | 88f | 94f |
| Gaitini et al [65], 2008 | Retrospective. Adult patients with suspected appendicitis. 132 patients also underwent CT. Clinical follow-up (inpatient only) for nonsurgical patients; indeterminate results excluded from analysis (n = 17). | 420 | 74 | 97 |
| Poortman et al [63], 2009 | Prospective. Adult patients with symptoms of appendicitis underwent US followed by CT for negative or indeterminate US. Clinical follow-up and inpatient observation for nonsurgical patients. | 151 (US) | 77 | 86 |
In the Dilley article, sensitivity and specificity were calculated for all (initial and repeat) US examinations performed during the studya and recalculatedb based only on final US findings (ie, the initial US if the findings were conclusive, or the definitive US in those patients who had multiple studies). In the study by Rettenbacher and colleagues, sensitivity and specificity were calculated for appendicitisc and for appendicitis + alternative diagnosis. d Doria and colleagues calculated 95% CIs for their performance metrics: esensitivity 95% CI 78%–87%, specificity 95% CI 90%–96%, fsensitivity 95% CI 86%–90%, specificity 95% CI 92%–95%.
Abbreviation: N/A, not applicable.