Standard Protocol Variables
| Category | Variable | Definition |
| Patient preparation | Medication withholding | Instructions are given for withholding prokinetic agents (metoclopramide, domperidone, and erythromycin), opiates, anticholinergic/antispasmodic agents, atropine, nifedipine, progesterone, octreotide, theophylline, benzodiazepine, and phentolamine. |
| Withholding time | Protocol clearly states that all of the above medications should be withheld for 2 d. | |
| Blood glucose | Instructions are given to test that serum glucose level is <200 mg/dL before the study. | |
| Blood glucose recording | Instructions are given to record blood glucose level and include in final report. | |
| Meal | Consensus meal | Meal is properly prepared using 118 mL (4 oz) of liquid egg white, 120 mL of water, 2 slices of toast, 30 g of jam or jelly, and no other ingredients. |
| Nothing by mouth | Protocol states that patient may not take anything by mouth for a minimum of 4 h. | |
| Meal ingestion time | Protocol directs that the patient should eat the meal rapidly (in <10 min). | |
| Partial meal | Protocol requires documentation of vomiting or of ingestion of only a portion of the meal. | |
| Radiopharmaceutical dose | The prescribed radiopharmaceutical is 99mTc-SC, and the dose is 18.5–37 MBq (0.5–1.0 mCi), | |
| Acquisition | Image projections | Both anterior and posterior images are acquired. |
| Image frequency | Images are acquired immediately upon meal completion and hourly until 4 h. | |
| Processing | Geometric mean | Instructions are given to calculate the geometric mean using anterior and posterior projections (geometric mean = √ (anterior counts × posterior counts). |
| Decay-corrected | Protocol includes instructions for decay correction of counts in region of interest. | |
| Percentage retention | Final measurements are reported as percentage of gastric retention at each time point. |