Growth hormone isoform testing in capillary dried blood spots: Results from single and multiple dose administration studies and large‐scale field collections

A multiphase study was designed to examine the detectability of human growth hormone (GH) use in capillary dried blood spots (DBS). First, 13 subjects self‐injected a single, 2‐mg dose of somatropin and collected capillary DBS samples for 24 h. Next, nine subjects self‐injected 2‐mg somatropin, six times over the course of 11 days; DBS were collected intermittently following dosing. Finally, a nondrug, large‐scale field study involved DBS collections from an athlete and staff population over 3 years. All DBS samples were self‐collected using the Tasso M20 device and were analyzed for the presence of GH using the WADA‐approved GH isoforms test. Following the single dose, positive detection within 12 h of dosing was 86% and 56% sensitive on Kits 1 and 2, respectively. In the multidose study, detection within 12 h was 85% and 69% sensitive on Kits 1 and 2, respectively. No positives were detected outside the 12‐h window following a single dose, wherein detection was 5.6% sensitive at 24‐h in the multidose study. Combining the 12‐h windows from both studies, 100% of samples had measurable recombinant (REC) and pituitary (PIT) GH concentrations above the assay LoD, 0.041 ng/ml. Finally, 1213 samples were collected in the large‐scale field study: 189 showed REC and PIT concentrations above the LoD; none returned positive results. GH is detectable in capillary DBS using the isoforms method for 12–24 h following use. While detection is short lived, transitioning to a DBS self‐collection method can allow more frequent testing and increase deterrence to GH abuse. Human growth hormone was administered to volunteers as either a single dose or multiple doses. Capillary blood was collected from all volunteers using the Tasso M20 device and tested using the GH Isoforms test. Growth hormone was detectable in capillary blood for up to 24 h following use.