Like Syl says it is the number of bacteria and the diversity of strains that determines efficacy. I personally don't feel ones that aren't tested aren't good. I feel the couple that have been tested may have been chosen because of many different reasons including money changing hands. If GI doctors always recommend VSL#3 it could be that company paid for it to be tested. I'm sure it is good but other brands may have been unable to get in trials, if you follow me.
-------------------- IBS-A for 20 years with terrible bloating and gas. On the diet since April 2004. Remember this from Heather's information pages:
"You absolutely must eat insoluble fiber foods, and as much as safely possible, but within the IBS dietary guidelines. Treat insoluble fiber foods with suitable caution, and you'll be able to enjoy a wide variety of them, in very healthy quantities, without problem." Please eat IF foods!