investigating interference in male testosterone immunoassays

1: Investigating interference in male testosterone immunoassays Darren Powell Project Supervisors � J.Kane + G.Waite Hope Hospital, Salford

3: Introduction 2: Testosterone Measurement Methods

Slide 4:And data published by others and reproduced by myself here shows that interference poses a serious problem for the measurement of female testosterone by direct immunoassay, resulting in huge amounts of positive bias in many samplesAnd data published by others and reproduced by myself here shows that interference poses a serious problem for the measurement of female testosterone by direct immunoassay, resulting in huge amounts of positive bias in many samples

6: Project Aims

Slide 8:This graphs shows the difference between direct and extracted testosterone versus an estimate of the testosterone based on the extracted result. What it clearly shows is that there is positive interference in the direct immunoassy, in that there is a a large number of results lying above the line of zero. What is of clinical significance is that this interference predominates at lower testosterone levels and might cause some men to have their diagnosis of testosterone deficiency missed. This graphs shows the difference between direct and extracted testosterone versus an estimate of the testosterone based on the extracted result. What it clearly shows is that there is positive interference in the direct immunoassy, in that there is a a large number of results lying above the line of zero. What is of clinical significance is that this interference predominates at lower testosterone levels and might cause some men to have their diagnosis of testosterone deficiency missed.

9: Results 2- Comparison of Direct Immunoassay for testosterone with HPLC-T/MS My next result shows a similar plot of how the direct assay fares against the T/MS method. For samples measuring > 10 nmol we see a reasonable agreement between direct IA and T/MS with most of the data points lying + - 20% of the T/MS result However for samples at the clinically important lower range (<10 nM Testo) we see large amounts of positive bias, and for some samples the difference is so great that I�ve had to artificially extend the y-axis.My next result shows a similar plot of how the direct assay fares against the T/MS method. For samples measuring > 10 nmol we see a reasonable agreement between direct IA and T/MS with most of the data points lying + - 20% of the T/MS result However for samples at the clinically important lower range (<10 nM Testo) we see large amounts of positive bias, and for some samples the difference is so great that I�ve had to artificially extend the y-axis.

Slide 10:The third of the graphs is the most interesting. We would have hoped to remove the effects of interference by extraction, However the graph shows us that there is significant interference, particularly at the lower end of the range in a few samples. This raises the question whether in some people there are hydrophobic interferents extracted into the ether with testosterone which interfere with the method. The third of the graphs is the most interesting. We would have hoped to remove the effects of interference by extraction, However the graph shows us that there is significant interference, particularly at the lower end of the range in a few samples. This raises the question whether in some people there are hydrophobic interferents extracted into the ether with testosterone which interfere with the method.

Slide 11:In conclusion, We have found that In conclusion, We have found that

12: Future Work Characterise the nature/causes of the interference in the measurement of testosterone by immunoassay, and their potential clinical significance.