Answer

Avoid NSAIDs for 7 days, avoid vitamin C in excess of 250mg for 3 days and avoid red meat for 3 days to minimize the possibility of false positives in gFOBT.

Explanation

Step 1: Recognizing the possible causes of false positives in gFOBT Guaiac-based fecal occult blood test (gFOBT) can yield false positive results due to various factors. These factors include the use of certain medications, dietary practices, and consumption of specific vitamins. Let's examine how NSAIDs, Vitamin C, and red meat can affect the results of gFOBT tests. Step 2: Understanding the impact of NSAIDs on gFOBT results Nonsteroidal anti-inflammatory drugs (NSAIDs) can cause gastrointestinal bleeding which may result in a positive test, even when no colorectal disease is present. It is recommended to avoid taking NSAIDs for 7 days prior to the gFOBT to reduce the risk of false positives. Step 3: Evaluating the effect of high Vitamin C intake on gFOBT results Vitamin C can oxidise the guaiac in the test, causing it to change color and potentially leading to a false positive result. Therefore, it is advisable to avoid taking more than 250mg of vitamin C for 3 days before the test. Step 4: Assessing how consumption of red meat can influence gFOBT results Red meat contains a type of iron that reacts with the reagents in the gFOBT test which can cause a false-positive result. It is recommended to avoid consuming red meat for 3 days prior to the test to mitigate the risks of incorrect results.