Prof. of Clinical Chemistry, Mansoura University

Implies a self – regulating process with an element of feed-back which detect any tendency to malfunction and readjusts the equipment so that it continues to function correctly.

Definitions and processing concepts: Continuous flow analyser: The reagent are pumped continuously by syring pump The samples are introduced at regular intervals The flow is segmented to separate one specimen from anothor This type is used as batch analyzer e.g technicon. Two types : a)single channel continuous flow: analyse one constituent in each specimen. b)Multichannel continuous flow: determination of several components in each sample

Discrete analyser: Samples are processed in separate reaction tubes. The instrument contain a variety of receptacle in which the sample and reagents are mixed. The reaction occurs: cuvettes, dry film slides. Some containers contain the reagents and only the specimen need to be added. Others add both reagents and specimen.

Reaction vessels and cuvets in discretes: Reused or discarded Used as cuvet or just reaction tube, aspirated in tube then to another tube for measurement For wash reused reaction vesseles or cuvets aspiration of the reaction mixture a detergent,alkaline or acid wash soln. is then dispensed into and aspirated out of the cuvets

Parallel analysis: All specimens are subjected to a series of analytical processes at the same time in a parallel fashion:  Discretionary multiple – channel analysis.  The specimen can be analyzed by any one or by more than one of the available processes (methods, channels).

- A number of specimens are processed in the same analytical session, or run:  Batch analyzer.

The components steps in automated system 1.Specimen identification. 2.Specimen preparation. 3.Specimen handling, transport and delivery. 4.Specimen processing. 5.Sample transport and delivery. 6.Reagent handling and storage. 7.Reagent delivery. 8.Chemical reaction phase. 9.Measurement approach. 10.Signal processing data handling and process control. These operations are usually performed sequentially but in some instrument, they may be combined and occur in parallel.

Specimen identification:

Specimen Preparation:

Specimen Handling, Transport and Delivery:

Specimen processing:

Sample transport and delivery: In continuous – flow system: the sample is aspirated through the sample probe into continuous reagent stream In Discrete analyzers: the sample is aspirated into sample probe and delivered, with reagent into reaction tube or cup.

Carry over: Carry over occurs when a previous sample or reagent contaminates successive tests in a run causing the next sample to have an aberrantly higher or lower results. Carry over occurs when anlytes occur in extremely high levels e.g. enzyme or h CG in pregnancy Carry over also occurs in systems that reuse cuvettes that are insufficiently washed after each testing cycle. In discrete systems with disposable reaction vessels and measuring cuvettes carry over is caused by the pipeting system

Disadv: one analyte per rotor but now recent models allow multiple analysis 24 rotors can be loaded at one time. In Continuous flow: by glass coils passing through the samples and reagents.

Measurement approaches: Spectrophotometry Fluorimetry e.g. IMX Chemiluminescenc e.g. IMMULITE Electrochemical for electrolytes

Examples:

Automated immunoassay systems differ from chemical analyzers in that they require the use of: 1.solid – phase reagents to separate bound and unbound 2.More sensitive detection methods e.g fluorescence and chemiluminescence 3.Special handling of the reagents: e.g. 1.Thermal conditioning to keep chemilum substrate stable. 2.Constant agitation to keep microparticles suspended.

4-Multiple Calibrators: (upto 6) Calibration usually nonlinear Example : ACS : 180 benchtop R-A Imm. AS.S ay IMMULITE : bench – top R-A Imm. Assay Automated immunoassay

Selection of instruments Role of an automated system in the workflow of the laboratory. Identification of candidate system (RA or batch). Cost effectiveness of the system. User-friendiness (interface between the machine and the human operator). Analytical performance.

Advantages of automation: Large number of samples may be processed with minimal technician. Two or more methods may be performed simultaneously. precision is superior to that of manual performance. calculations may not be required.

Disadvantages of automation: limitation of the methodology "closed system". Expensive. Many systems, are impractical to use for small numbers of samples. Therefore, back up manual methods may be required for individual emergency analysis. Back up methods must also be available in the event of instrumental failures.