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Hello Helen We have used commercial antibody binding tubes (Scantibodies), precipitation with animal sera and dilution studies - see Ann Clin Biochem 1998; 35: 317-320 if you want brief details of the methods which are very simple. However we now find fewer problems with the ELECSYS than our earlier analyser. I must confess that now if I get an occasional odd result, I find it easier to send suspect samples straight to Penny Clark in Birmingham. This has the advantage that they can check the results on a different method/analyser (assuming they haven't just gone over to Roche as well!). They will also perform HAMA/ heterophile ab checks on request, do a free T4 by equilibrium dialysis if a definite result is needed, and occasionally if needed can look for other interference such as anti-thyroid hormones. If the FT4s you are querying are at the low end of the reference range, I wonder if this is a conceptual problem caused by changing from a previous method that gave FT4 results lower compared to the reference range than the ELECSYS. With any method I have used, there has always been a certain proportion of high TSHs with low normal FT4s, which has been put down to either mild hypothyroidism (TSH presumably being more 'sensitive' and rising first), or to subclinical hypothyroidism (possibly the same thing). If the FT4 results are normal or slightly high, I suggest you need to make sure the patients really aren't on thyroid treatment. We have several otherwise intelligent GPs and clinicians who are reluctant to include this useful information on their request forms, which is often a problem when it comes to interpretation and selection of further tests. Hope that helps Steve Dr S Frost -----Original Message----- From: Smith, Helen [mailto:[log in to unmask]] Sent: Tuesday, May 08, 2001 3:43 PM To: Subject: Checking for HAMA antibodies Dear Colleagues, I realise this is probably an old problem, but your help would be appreciated. We are seeing a fairly large number of slightly raised TSH results with 'normal' free T4, in patients not apparently on thyroxine, using the Roche Elecsys 2010. We have the feeling this could be due to the presence of HAMA, but Roche claim to have virtually eliminated this problem by use of a human/mouse chimeric antibody. Can anyone suggest a simple way to check our samples for HAMA? I've heard of PEG precipitation or dilutions to check for linearity of response, but I'd like to know what other people are doing. Many thanks Helen Smith