Comparison of cost of preparing reagents in laboratory with cost of using commercial kits.

A comparison of the cost of laboratory-made reagents with that of commercial kits was made for three serum-enzyme estimations and three serum-hormone estimations. The cost of reagents in kit form could only be justified on economic grounds for serum aspartate transaminase, alanine transaminase, and lactic dehydrogenase if the laboratory performed less than about 35 tests per day. It is unlikely that the use of kits for serum tri-iodothyronine, thyroxine, and thyrotrophic hormone can be justified on economic grounds for any workload. It is estimated that between 2 million pounds and 3 million pounds is spent unnecessarily by the National Health Service each year to purchase commercially prepared reagents for the six tests studied.