Final answer:
The preexamination or preanalytical phase includes the initial steps taken to ensure the integrity and quality of biological samples for laboratory testing. This phase covers blood collection and preparation, surgical procedure reviews, and the establishment of adequate preanalytical conditions, such as chromatographic setups and stability assays for precise data.
Step-by-step explanation:
Preexamination or Preanalytical Phase in Laboratory Medicine
The preexamination or preanalytical phase is a critical component of laboratory testing where the quality and integrity of biological samples are established. It encompasses all the steps taken before the actual analytical process begins. Examples of preanalytical procedures include the collection of blood samples into proper containers like tubes containing K2EDTA and their subsequent centrifugation to obtain plasma. For certain analyses, plasma samples may be quenched with methanol to stop any further metabolic reactions. On the other hand, urine samples might undergo analysis with no preparation prior to the actual testing process.
Other preanalytical components involve the review of surgical procedures by medical teams, ensuring patient identification, and confirming surgical sites. For example, prior to a surgery, the nursing staff must confirm sterility and availability of necessary equipment. This also includes the analytics staff reviewing the sample preparation procedures, such as pretreating plasma with SPE (Solid Phase Extraction) and the evaporation of eluents for certain tests. Even the reconstitution of dried residues in solvents such as methanol for analysis falls under preanalytical work.
Also included in this phase are preparations and reviews of chromatographic conditions and stability assays essential for guaranteeing precise and accurate data. This is crucial, especially when working with in vivo studies quantifying drugs or metabolites, which often require complex sample preparation protocols. Such protocols ensure that endogenous and exogenous compounds are reduced or eliminated, enhancing the sensitivity of the methodologies used.