In the realm of clinical diagnostics, the integrity of laboratory testing is paramount. Quality controls (QCs) and external quality assurance (EQA) materials are essential tools that help laboratories validate and maintain the accuracy of their diagnostic tests. The choice between lyophilised and liquid stable (frozen or refrigerated) quality controls can significantly affect the reliability of diagnostic outcomes. This article provides an in-depth analysis of why lyophilised quality controls are superior, focusing on their ability to closely match patient specimens, logistical advantages, enhanced stability, and operational efficiency.
Mimicking True Patient Specimens
The primary objective of any QC or EQA material is to replicate the characteristics of patient specimens as closely as possible. The addition of synthetic stabilisers in liquid stable controls introduces multiple variables that deviate from patient specimens’ natural composition. These additives can affect the test results by altering the chemical behaviour of the biomarkers being measured.
Lyophilised quality controls, however, typically undergo only one significant alteration—the lyophilisation process. This process has been rigorously studied and shown to minimally impact the biological and chemical properties of the sample. For example, the Royal College of Pathologists of Australasia Quality Assurance Programs (RCPAQAP) conducted a study that demonstrated that lyophilised serum chemistry controls maintained a high degree of similarity to patient samples for crucial measurands like electrolytes, enzymes, and other biochemical markers. The study indicated minimal variability in recovery and commutability post-lyophilisation, supporting the effectiveness of lyophilisation in preserving the integrity of the samples – Investigating the Effects of Lyophilisation on General Serum Chemistry EQA Material for Routine Measurands. Further studies across other disciplines had similar findings – Review of lyophilisation of external quality assurance program material.
Case Study: Lyophilisation in Endocrine Testing
A specific case where lyophilised materials have proven particularly beneficial is in the field of endocrine testing. Hormones are notoriously unstable and prone to degradation when stored in liquid form – Effect of lyophilisation on measurement of selected endocrine analytes. Lyophilised hormone controls provide a stable matrix that preserves the structural integrity and bioactivity of these delicate molecules over extended periods. The stability ensures that when reconstituted, the control material exhibits the same hormonal properties as those present in actual patient blood samples, leading to more accurate hormonal assays.
Logistical and Operational Benefits
Reducing the Cold Chain Dependency
One of the most significant logistical advantages of lyophilised quality controls is their independence from the cold chain. Unlike liquid controls, which require continuous refrigeration to prevent degradation, lyophilised controls can be stored and transported at room temperature without compromising their stability. This feature is particularly advantageous for laboratories in remote or resource-limited settings where refrigeration facilities are inadequate or unreliable. Additionally, it results in considerable cost savings related to transport and storage, while also reducing the environmental impact associated with refrigerated shipping.
Enhancing Stability and Shelf Life
Lyophilised materials are not only stable at higher temperatures but also less susceptible to microbial contamination and degradation over time. This enhanced stability translates into a longer shelf life, reducing the frequency of control replacements and ensuring consistent test results over longer periods. Studies have shown that lyophilised controls can remain stable for years, whereas liquid controls often exhibit variability after just a few months.
Lyophilised quality controls offer numerous advantages over liquid stable formats, making them an increasingly popular choice in clinical diagnostics. Their ability to closely mimic patient specimens, combined with logistical and operational efficiencies, positions them as a key component in the future of laboratory medicine. As technology and research continue to evolve, the role of lyophilised controls is expected to expand, further enhancing the accuracy and reliability of diagnostic testing across the globe.
