Criteria for the assessment of analyser practicability

This article lists the theoretical criteria that need to be considered to assess the practicability of an automatic analyser. Two essential sets of criteria should be taken into account when selecting an automatic analyser: ‘reliability’ and ‘practicability’. Practibility covers the features that provide information about the suitability of an analyser for specific working conditions. These practibility criteria are classsified in this article and include the environment; work organization; versatility and flexibility; safely controls; staff training; maintenance and operational costs.


Introduction
This paper describes the theoretical criteria that need to be considered in order to assess the practicability of an automatic analyser for eventual use under specific working conditions. The criteria to be considered in selecting an analyser are reliability and practicability.
Reliability can be defined as the ability an analyser has to maintain a good analytical quality (imprecision, inaccuracy, shift etc.) on a long-term basis.
Practicability includes a number of qualities that provide intbrmation about the whole range of possibilities the analyser has under the specific working conditions of a given laboratory.
An analyser will be selected on the basis of manufacturers' technical information, the experiences of other users and published evaluations. A good evaluation will cover all aspects ofanalysis, both thvourable and unfavourable, and provide potential users with the information that will allow them to select the instrument that best suits their specific working requirements.
'Practicability' criteria can be classified as follows: Need for water (distilled, de-ionized) outlet; and consumption per hour.
Air-conditioning and environmental temperature proper functioning. Need for drains: reagent removal, automatic or manual. Compressed air. Noise, in decibels, from the analyser and printer (within permitted levels).
2. Work organization 2.1. Start operations Time required by the analyser to start any kind of analytical process.
Eventual automatic programming of start operations. Length of time devoted daily to analyser tuning operations (before the analysis itself). for processing samples on an emergency basis and interference with the previously planned workload. Processing of samples of urine and other biological fluids. Use of primary tube, tubes, cups and microcups on the same sample holder.

Sample identification
Without bar-code.
Label with bar-code on sample holder. Label with bar-code on primary tube. Use of labels with bar code: with the operator taking part in the reading (with optic laser, scanner, etc.); without the operator taking part in the reading: reader built into the sample holder that identifies the sample, versus the optic laser which is located in the analyser (this is the most reliable and safest kind of identification). Assessment of sample identification system. Assessment of deficiencies in bar-code reading. Is it essential to have the label on the tube; is the proper position key to the proper reading; to what extent does label decay matter etc.?

Sample aspiration
Sample aspiration from the cup. Sample aspiration straight from the primary tube; eventual use of different sizes.
Eventual sample aspiration from a closed primary tube.
Prerequisites for the use of primary tubes.
Effectiveness of fibrine detectors and sample level detectors.
Sample dead volume.
Washing of sample pipette (inside and outside) to prevent sample/sample, reagent/reagent or both kinds of contamination.

Reagenls
Needs preparation or is ready-to use.
Storage in the reagent compartment of the analyser, cooled or not, or outside the reagent compartment. Time devoted to stopping the sampling process while working on a routine basis in order to calibrate or refill with reagents.
Stopping: immediate availability without a time delay.

Information processing
Assess data entered through keyboard and their difficulty.
Editing: one patient at a time, by a series ofresults, or both.
Possibility of programming the edition format of results.
Possibility of visualizing results on the screen even when incomplete.
Ability to correct and validate patient's results on the screen.
Possibility of adding the results of other measurements to the final report.
Eventual search of a patient on the analyzer file by laboratory number, identification number or other demographic data, in order to review him on the screen or re-edit it.
Possibility of fast editing of a patient's report if required tests are performed before those of a previous patient.
Filing capacity (patients and results).
Possibility of setting up a bidirectional connection with the central computer. Transmission speed.
Open analytical system: free choice of reagents; ability to adapt reagents and methods not initially anticipated. Closed analytical system: possibility of a dialogue between the manufacturer and the user about methods, reviews and program changes; Use of methods recommended by international clinical chemistry organizations. Acceptance decided by the operator.
Absorbance control of reaction blanks.
Printing of results with alarm signal if they go beyond linearity limits. Regular revision of programmes. Possibility of programme expansion, as well as changes and subsequent improvements.
After sale technical service.
Other working controls; self-diagnosis programme.
Frequent breakdown (ask the users).
Speed with which the technical service responds when the analyser breaks down or stops.