Analytical Instrumentation Laboratory: EasyRA

Automation in Clinical Chemistry

The analytic phase is the most automated stage, where actual measurements and analysis occur.

The analytical process in clinical chemistry consists of three phases

Preanalytic, Analytic, and Postanalytic.

Advantages of Automation

• Speed of analysis;

• reduction in human error;

• increased reproducibility;

• decreased sample and reagent volume; decreased cost of consumables;

• lower cost per test overall.

Basic Approaches with Automated Analyzers

There are three basic approaches:

• Continuous Flow Analyzers

• Centrifugal Analysis

• Discrete Analysis.

Continuous Flow Analysis

Continuous Flow Analyzers (mostly obsolete) pump liquids—reagents, diluents, and samples—through a continuous tubing system. Air bubbles are introduced at regular intervals to separate samples.

Continuous Flow Analysis Disadvantages

Does not allow individual test selection; it must operate continuously even when no tests are running; it consumes reagents constantly; and it must be monitored for carryover problems.

Centrifugal Analysis

• Samples and reagents are added to a centrifugal cuvet with three compartments: sample, reagent, and reaction mixture.

• Mixing occurs when the rotor spins rapidly and then stops suddenly.

• Cuvets pass through the optical path of the spectrophotometer for measurement.

*Only one test can be performed at a time.

Discrete Analysis (Principle)

• Each sample and its reagents are kept separate in their own container.

• Containers are disposed of after analysis.

• Uses a random access hydrofluorocarbon liquid to reduce surface tension between reagents and tubing, minimizing carryover.

• Keeps carryover minimal but increases cost per test due to disposables.

*Capable of running multiple tests on one sample or one test on multiple samples.

Discrete Analysis Sample 1:

Glucose, electrolytes

Discrete Analysis Sample 2:

Total protein, calcium

Discrete Analysis Sample 3:

Triglycerides, cholesterol, glucose

Discrete Analysis Sample 4:

Bilirubin, total protein

Reagent Handling

Reagents are stored either at room temperature or in refrigerated compartments.

Reagent Handling - Open Reagent System

Accepts reagents from outside suppliers.

Reagent Handling - Closed Reagent System

Accepts reagents only from the manufacturer (more expensive).

*The Medica EasyRA uses a closed system.

Medica EasyRA Components

Touch Screen/Monitor, Computer, Reagent/Sample Area, Transfer Arm/Probe, Reaction Area, Electronics Panel, and Fluidics Drawer (Diluent/Waste).

Clinical Chemistry Tests on EasyRA

Enzyme levels (Liver function tests: ALT, AST, ALP), Ion levels (Na+, K+, Li+, Cl−), Glucose, Total Protein/Albumin, and Cholesterol.

Acceptable Sample Types

Serum, Plasma, Diluted Blood, Urine, and Diluted Urine.

Reagent Wedges

Each wedge contains an RFID (Radio Frequency Identification) chip embedded in the label. The RFID reader in the Reagent/Sample Area reads data including reagent parameters, lot information, and number of tests remaining on each wedge. This ensures reagent tracking and prevents errors.

Reaction Area

Contains a Cuvette Carousel that holds up to 72 individual cuvettes. The probe dispenses both samples and reagents into these cuvettes. The carousel turns at precise times, allowing each cuvette to pass the photometer for measurement.

Photometer Details

Contains six interference filters. Measures light at seven wavelengths: 340, 405, 520, 550, 600, 660, and 700 nm.

*Uses a Xenon Flash Lamp as the light source for optical readings.

Heated Air Bath

Maintains the air around cuvettes at 37°C ± 0.25°C, ensuring all reactions occur at a predefined and consistent temperature for accuracy.

Transfer Arm / Probe

Picks up reagents and samples and deposits them into cuvettes or the ISE module. Mixes reagents and samples by injecting air into cuvettes. Receives diluent from the dilutor pump to clean the probe and flush waste into the wash cup, preventing contamination.

Flow of Fluids: Diluent Path

Illustrates the flow of fluid from the diluent bottle to the probe, preparing it for analysis.

Flow of Fluids: Waste Path

Illustrates flow from the probe to the waste bottle, disposing of used fluids after analysis.

Daily Maintenance Tasks

Daily Cleaning: Clean probe and calibrate ISE module.

Daily Inspection: Check dilutor pump, probe, waste/diluent, and pump tubes. Priming: Prime the diluent line and ISE Cal A/B to prepare the system for use.

Quality Control Requirements

Run two levels of QC material daily for each chemistry performed. Perform weekly EasyRA Precision Test to check photometer and pipette precision. Participate in External Quality Control programs such as the College of American Pathologists (CAP).

Method Validation Standards

Before reporting results, laboratories must validate accuracy, precision, reportable range for each test, and verify that Medica's reference intervals fit the lab's patient population.

Detection Methods

Based on absorbance/transmittance photometry. Each analyte is measured at specific times and wavelengths. Ions: Measured via ion-selective electrodes (ISEs) comparing voltage against a silver/silver chloride (Ag/AgCl) reference electrode—this is a form of potentiometry.

Detection Methods Enzymes

Determined by the rate at which they change one colored substance into another.

Detection Methods Ions

Measured via ion-selective electrodes (ISEs), comparing voltage against a silver/silver chloride (Ag/AgCl) reference electrode—this is a form of potentiometry.

ISE Principle

The ISE determines the ion concentration by measuring electrical potential differences across selective membranes, reflecting ion activity in solution.