Final answer:
Blood samples that are prone to metabolic changes post-collection, such as those containing ammonia, lactic acid, or certain hormones, need to be placed in an ice bath within 30 minutes of collection to preserve their integrity for analysis.
Step-by-step explanation:
A phlebotomist should place certain specimens in an ice bath within 30 minutes after collection to preserve the integrity of the sample. Specifically, blood samples that require the determination of volatile substances or are prone to metabolic processes that can alter the analyte in question, such as ammonia, lactic acid, or certain hormones, need to be chilled promptly. Additionally, samples like plasma obtained from blood collected into heparin tubes require rapid cooling to slow down enzymatic processes that might change the composition of the sample. An ice bath helps to maintain the stability of the analytes until they can be analyzed.
Stabilization of Specimens
When blood samples are collected into tubes containing lithium heparin and centrifuged to obtain plasma, placing them in an ice bath helps prevent the continuing cellular metabolism, which may impact the results of certain tests - particularly those where the metabolite levels can change rapidly after collection. Similarly, samples involving K2EDTA and pretreatment such as plasma pretreatment by SPE (Solid Phase Extraction), need to be maintained at a controlled temperature to ensure accurate test results.
The process of blood collection itself, as described in Figure 10.21, is critical for medical analysis and the post-collection handling is just as important. Ensuring the sample is promptly chilled can be the difference between an accurate and a compromised test result.