"Had one done in Sydney (Australia) a few years ago, which came back all fine."
>>>On what basis did it 'come back all fine'? Do you mean you, or a health practitioner, interpreted the 'mercury' data reading as 'nil' or 'close to nil' ?
It is very inappropriate to assume that test data for toxic elements such as mercury are overtly accurate. It can be overtly accurate (i.e. the stated reading for mercury really can be an accurate reflection of body burden of mercury), but quite often this is not, in fact, the case. This common misnomer of just reading the results directly as they appear on the results and assuming it to be accurate is fallen foul of by many professional practitioners, not just laypersons:
Better-informed practitioners, however (and they're in the minority), are aware that many people under the influence of mercury intoxication are in fact very poor excretors of mercury, not least because mercury leads to dysfunction of the very excretory mechanisms which the body relies upon to excrete mercury. Therefore, it is very common for someone's hair to exhibit exceedingly low levels of mercury, even if they may be in a mercury intoxicated state. This is why it is so important to perform statistical analyses on the readings for non-toxic elements. In cases where a person is mercury intoxicated but shows a low overt reading for mercury per se, there will tend to be a specific pattern in the distribution of their non-toxic/essential elements. This is because mercury is ALSO capable of disrupting the transport of minerals around the body via cellular membranes. Thus, any such disruption/derangement of mineral transport may be visible in skewed results for essential elements, as I touched upon in my earlier post (Andrew Cutler's 'Hair Test Interpretation' book).
"The local hospital's tests for elastase came back normal (actually in a 'possible problem' range, however the gastrologist says there is no reason to suspect pancreatic problem. Unfortunately he now disregards the rest of the Metametrix test results, as well."
>>>What about symptoms - for example, does your son or daughter suffer from above-average degree of flatulence? (sorry, no other way to put it)
Any dental decay? Gum disease? Undigested food in stools?