Gastric Emptying Scintigraphy: Diagnostic Value of Delayed Imaging and the Impact on Reclassification of Diagnosis.

Objectives: To investigate the added diagnostic value of delayed imaging at 3 and 4 h compared to 2 h imaging as well as scanning up to 4 h compared to 3, and by this means, diagnosis reclassification or changes in diagnosis across various time points.

Methods: Seventeen patients clinically suspected of gastroparesis, 8 (47.1%) men and 9 (52.9%) women, according to the standard procedural guidelines, underwent gastric emptying scintigraphy after ingesting a standard meal. One-minute static images in anterior and posterior projections were acquired immediately after ingestion and then at 1-, 2-, 3- , and 4 h time points. For image analysis, a manual region-of-interest was drawn, and then, count of stomach in each projection was used to calculate geometric mean for each time point. Decay correction was applied. At 2-, 3- and 4 h time points, percentage of retained activity was compared to standard values; therefore, each patient was labeled as normal or delayed.

Results: Pairwise correlation between time points was statistically significant. Value of hour 3 shows an extremely strong correlation with the value of hour 4 (r=0.951, p<0.001). In hour 2, of 17 participants, 11 (64.7%) were diagnosed as normal and 6 (35.3%) as delayed. In hour 3, the diagnosis made as delayed rose to 9 (52.9%), whereas normal was 8 (47.1%). Finally, in hour 4, results were 10 (58.8%) as delayed and 7 (41.2%) as normal. All subjects who were labeled as delayed in hour 3 remained with the same diagnosis and 1 out of 8 subjects categorized as normal in hour 3 changed to delayed. For testing agreement, coefficient of kappa was computed between each pair. Agreement between diagnosis in hour 2 with hours 3 or 4 was not strong (kappa <0.6 for both pairs). However, a strong agreement was found between diagnosis in hours 3 and 4 (kappa: 0.881).

Conclusion: Because of excellent correlation between values of hours 3 and 4 and strong agreement between the diagnosis in those time points, extending acquisition from 3 to 4 h adds little to the final dai gnosis and may not be noticeably meaningful, especially in the clinical setting.