A collaborative study to establish the second international standard for streptokinase

A long-standing reference for streptokinase activity has been in use since 1965. This reference, known as 62/7, has supported the calibration of high-purity clinical batches. However, the need for a more modern standard became apparent. No prior work had resolved the limitations of the older standard. The current standard may not meet modern analytical requirements. Scientists recognized the importance of a new high-purity reference. The World Health Organisation plays a key role in such standardization efforts. This gap motivated a collaborative international study.

The goal was to identify a suitable replacement for the existing streptokinase standard. A new high-purity standard was needed to ensure accurate potency testing. Six laboratories participated in this collaborative effort. The study compared two candidate preparations with the current standard. The researchers aimed to assess both potency and stability. The clot lysis assay was selected as the primary method for comparison. This approach allowed for a direct evaluation of activity levels. The study also considered practical aspects like dosage per ampoule.

The study used a clot lysis assay to measure streptokinase activity. Two candidate preparations were tested alongside the current standard. The six participating laboratories followed a standardized protocol. Each lab conducted the same type of potency testing. The researchers compared the results across all sites. Accelerated degradation tests were also performed. These tests assessed the long-term stability of each preparation. The data from all methods were synthesized to determine suitability.

Preparation 88/826 showed a potency of 671 i.u. per ampoule. Preparation 88/824 had a lower potency of 461 i.u. per ampoule. Both preparations were found to be suitable as standards. However, 88/826 was preferred due to its higher activity level. Each ampoule of 88/826 contains a more usable amount of activity. Stability tests confirmed that 88/826 remains effective over time. The WHO assigned a potency of 700 i.u. to the selected preparation. This value reflects the average potency observed in the study.

The study identified a new high-purity streptokinase standard. Preparation 88/826 was selected as the preferred candidate. The researchers propose that this preparation is more suitable for testing. The WHO officially adopted 88/826 as the second international standard. The assigned potency of 700 i.u. per ampoule is based on the study results. The stability of 88/826 supports its long-term use. The study suggests that this standard improves the accuracy of potency testing. The authors propose that this standard will enhance global consistency in streptokinase calibration.