Lecture 1 - Biochemical Tests in Medicine Flashcards
What are the primary objectives of biochemistry labs in providing medical results?
Biochemistry labs aim to provide timely, accurate, reproducible, and relevant results. They also offer expert interpretative advice to clinicians, such as accepting or rejecting results.
List four essential purposes of biochemical tests in medicine.
Biochemical tests in medicine serve four main purposes: Diagnosis, Prognosis (predicting disease outcomes), Screening for undiagnosed conditions, and Monitoring treatment and disease progression.
When delivering samples to the lab, what factors are crucial for ensuring accurate testing?
Crucial factors include ensuring the appropriate sample is collected, using the correct tube, employing the right collection method, taking the sample at the appropriate time, completing the request form accurately, and delivering the sample promptly to the lab.
Explain the significance of Potassium Oxalate and Sodium Fluoride in blood glucose analysis.
Potassium Oxalate is an anticoagulant that binds calcium ions, and Sodium Fluoride inhibits glycolysis, maintaining glucose and lactate concentrations. This is important in diagnosing diabetes, where the reference interval is 4.0-6.0 mmol/L.
What is the reference interval, and how is it determined for a particular analyte?
The reference interval is chosen to include 95% of values from healthy volunteers, meaning 5% of the normal population will be outside this range.
What are the two spectrophotometric methods for measuring blood glucose concentration, and how do they work?
The two methods are Assay 1 (Direct chemical reaction) and Assay 2 (Enzyme-linked reaction). In Assay 1, glucose reacts with a chemical (e.g., dinitro salicylic acid) to produce a colour change. In Assay 2, glucose oxidase oxidizes glucose, releasing hydrogen peroxide, which reacts with 0-Danisidine to produce a coloured product.
Name and define the key parameters that need to be assessed for each assay in biochemistry testing.
Key parameters include analytical sensitivity (detectable amount of analyte), analytical specificity (ability to detect a specific substance), accuracy (closeness to the true value), precision (reproducibility of measurements), and limits of linearity (range of accurate concentrations).
How can regression analysis be used in comparing the output of two different assays?
Regression analysis involves plotting concentration values obtained from Assay 1 against those from Assay 2 to assess their agreement and correlation.
What does a Bland-Altman plot indicate, and how is it interpreted?
A Bland-Altman plot indicates the agreement between two assays. It plots the difference between Assay 1 and Assay 2 values against the mean value. Interpretation involves assessing the level of agreement and bias between the two assays.
Describe the different tubes used for blood collection, their color coding, additives, and clinical uses.
here are various tubes for blood collection, each color-coded for specific purposes. Here are the details:
Red: Contains a clot activator; used for serum biochemistry, drug monitoring, and serum immunology tests.
Yellow: Also contains a clot activator with gel; used for serum biochemistry, drug monitoring, and serum immunology tests.
Lavender: Contains K3 EDTA or K2 EDTA; used for haematology tests.
Black: Used for ESR (Erythrocyte Sedimentation Rate) tests.
Grey: Contains Sodium Fluoride + Potassium Oxalate; used for glucose tests.
Light Blue: Contains Sodium Citrate (3.2%); used for coagulation tests.
Green: Contains Lithium Heparin; used for emergency biochemistry and plasma biochemistry tests.
What is the purpose of determining a precision profile across two assays in biochemical testing?
Determining a precision profile involves calculating the Coefficient of Variation (CV) at different analyte concentrations. This helps evaluate the precision and reproducibility of two different assays, aiding in quality control and assessment of measurement variability.
Define the detection limit in biochemical testing.
The detection limit is the lowest amount of analyte that can be distinguished from the absence of the analyte in a sample. It marks the lower boundary for accurate detection.
Explain the concept of quality control (QC) and the role of internal quality control.
Quality control (QC) involves processes to ensure that analyzers provide precise and accurate results. Internal quality control involves the use of control materials with known analyte concentrations tested on the machines. Data is plotted on Levy-Jennings plots to monitor instrument performance.
What is a Levy-Jennings plot, and how is it used to monitor the quality of lab results?
A Levy-Jennings plot is a graphical tool that helps monitor the quality of lab results. It displays changes in the concentration measured from QC materials over time, allowing the identification of trends and shifts, which can signal issues in accuracy and precision.
What is the significance of point-of-care testing in medical laboratories?
Point-of-care testing involves performing laboratory tests near the patient, allowing for immediate care and treatment decisions. It is valuable for rapid diagnoses and monitoring of conditions, particularly in critical or emergency situations.
