Antibodies also like room temperature
Exact compliance with the stipulated temperature is crucial in rapid tests such as those often performed in hospitals and in pregnancy or drug tests. This has been emphasised by BAM Federal Institute for Materials Research and Testing scientists. Tests at refrigerator temperatures lead to different results than those at room temperature. BAM's analytical chemists have investigated the influence of temperature on sensitivity and precision of the results of immunoassays and have recommended tests at room temperature.
Immunoassays are based on the specific binding between antigens and antibodies. The method is not only used in rapid tests in the field of medicine, but also in food and environmental analysis. Immunoassays are becoming less expensive and are therefore found a wide application.
The scientists have examined a specific test, the so-called hapten immunoassay. These assays are carried out in several steps where time and temperature are in principle variable. Sometimes even the person performing the test cannot directly influence these settings, for example the laboratory room temperature. So far, little was known as to which of the many steps involved in performing immunoassays were really sensitive to temperature.
Based on extensive studies at different temperatures, BAM scientists recommend performing the tests at room temperature. "This is at the expense of the sensitivity of the test, but the disadvantage of using 21 degrees Celsius is more than compensated by increased precision," says BAM bioanalysts Rudolf J. Schneider.
The influence of temperature was tested for two active pharmaceutical agents: caffeine and carbamazepine. Carbamazepine, an anticonvulsant, and caffeine are used in environmental analysis as indicators in aquatic surveys. Additionally, two different substrates as well as two different detection methods were used: photometry and fluorometry. Identical results were found: temperature influenced the parameters studied only in the so-called competition step. Temperature affects the result's uncertainty, the detection limit, and the measurement range.
The results are clear: the best results can be obtained when reagents, solutions and microtiter plates often used in diagnostics, are kept at room temperature around of 21 degrees Celsius, and all assay steps are performed at this temperature.