Hold The Train… 12-Hour Test May Not Be Best Answer
Jim Prevor’s Perishable Pundit, August 1, 2007
In our piece, Church Brothers/True Leaf Recalls, Then ‘Unrecalls’ Spring Mix/Arugula After Testing Mishap, we urged the end to “test and release” in favor of “test and hold” in this paragraph:
…this business of testing finished product and releasing the product before the test result is back is a disaster waiting to happen. There are new 12-hour salmonella tests being required by McDonald’s and already in use by companies such as Earthbound Farms. They should become the industry standard, and the practice should be test and hold — release only after the results are in. Most product doesn’t ship out the instant it comes off the line, so this 12-hour test is not going to pose many problems.
We may have jumped the gun a bit. In theory it is a good idea but there are some unanswered questions on the matter. One processor sent us this note:
After reading the Pundit on True Leaf and the false positives, I couldn’t help but think there may be an issue regarding the effectiveness of the 12-hour PCR based tests on the market. Many in the industry, us included, are using it based on pressure from accounts and not necessarily based on scientific accuracy. The PCR is a presence / absence test, that looks for genetic material of e-coli and salmonella. It does not tell you if the cells are dead or alive, if it was one or one million cells, or if the genetic material was from a current or past event (i.e., a bird strike on the ground 12 months ago).
The developer stands behind the results and is very reputable so there is no issue from that standpoint. However, no one seems to have the scientific data (at least it’s not shared) that helps us determine the true accuracy. We all know painfully well the rate of false positives with the conventional testing methods. There was also a symposium held May 31, in Chicago, in which FDA and CA Dept of Health participated. One concern raised was the accuracy of the PCR test based on the very limited data complied and the speed at which the industry is ramping it up.
Albert Einstein is said to have said that “Everything should be made as simple as possible, but not simpler.” Equally, food safety efforts need to move ahead as fast as possible, but not faster.
Without good data on false positives and false negatives we just don’t know what our test results will mean. Maybe this piece can elicit some input from someone with access to more information on the PCR test. The industry needs to know where this train is going before we buy our ticket.