organizational aspects of selective analysers

Journal of Automatic Chemistry Vol. 10, No. 4 (October-December 1988), pp. 184-187

Organizational aspects of selective analysers

T. D. GearyInstitute ofMedical and Veterinary Science, Adelaide, South Australia, Australia

It was intended that this symposium should provideinformation to assist laboratory staff to understand a fewof the characteristics of analytical systems. This paperwill concentrate on the importance of sample identifica-tion and bi-directional interfacing, the relative merits ofselectivity against batch selectivity, a review of thequality-control needs ofthe newer analysers, and, finally,the paper will address the advantages and disadvantagesof open and closed systems. These characteristics shouldbe considered when selecting analytical instruments forthe laboratory.

The selection process adopted by the laboratory prior topurchase requires a careful review ofthe characteristics ofthe intruments under consideration and a clear definitionof the problem the laboratory wishes to solve by thepurchase. There are several publications in the literaturewhich discuss procedures to follow in order to define thelaboratory’s problems and then to find an analyser mostsuited to help solve the problems so defined. The ExpertPanel on Instrumentation has published papers from a

symposium [1] on the topic and a brief review of theprocedure suggested would not be out of place in thecontext of the present publication. A decision strategywas outlined by Professor Buttner in the previoussymposium and it is intended here to concentrate on twoof the points made: the definition of the problem and theinteraction with the infrastructure.

Professor Buttner’s discussed non-monetary criteria to beused in the selection process and provided a listing ofpoints relating to the practicability of the instrument.These points are listed below:

(1) Space requirements.(2) Energy consumption, other service requirements.(3) Ease of operation.(4) Adaptability and change-over of analytical

methods.(5) Possibility of introducing urgent samples into

routine procedure.(6) No restriction in terms ofthe selection ofreagents.(7) Safe operation.(8) Fault detection and signalling.(9) Full operating instructions.

(10) Environmental aspects, for example productionof effluent.

An understanding of the topics discussed in that presen-tation will assist with the collection of data on theimportant points, such as ease of operation, adaptabilityof methods, handling of the urgent specimen, open orclosed systems, fault detection and signalling the fault.

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The interaction with the infrastructure is a difficultsubject for it is often hard to predict the effect that anyalteration in the laboratory organization will have on thehandling of the workload, particularly when one consid-ers the wide ranging changes positive identification,bi-directional interfacing, selectivity and the computingpower of modern analytical systems do have on theoperation of a laboratory.

When analysing the total effect the purchase of a newsystem will have, importance should be placed uponpositive identification. The advantages provided bypositive identification of all steps from specimen collec-tion to sample presentation to the analyser should beappreciated. The International Federation of ClinicalChemistry and the European Committee for ClinicalLaboratory Standards have a Working Party with amandate to consider specimen identification. This ischaired by Professor Bonini and a draft documentproduced by the Working Party contains details of thevarious approaches taken to positive identification.However, attempts to provide a total hospital positivepatient identification scheme have not been particularlysuccessful. This is unfortunate for the potential value ofsuch a system is great. The manufacturers have tended toconcentrate upon systems for positive identificationwhich begin when the specimen reaches the laboratory.These systems provide the laboratory with a number ofadvantages but even they cannot be fully implementedwithout the availability of bi-directional interfacing(figure 1). The communication between computerspresents something of a problem which can only beovercome by further standardization of the communica-tion protocol.

Patient Demographics

CentralComputer

Selection of Tests

identification

Specimen---Sample----Test PortionAnalyserFigu 1.

Report"Generation

The flow diagrams of both selective analysers andselective batch analysis are shown in figures 2 and 3. Asthese diagrams indicate there are advantages in the use ofthe direct selective analysis against the selective batchanalysis. These advantages include the following:

T. D. Geary Organizational aspects of selective analysers

BATCH SELECTIVITY

ON BOARD COMPUTER

ORGANISATION OF BATCHES

INDIVIDUAL RESULTS

COMPILED

CENTRAL COMPUTER

S_ELECTI ANALYSERS

ROUTINE

ON BOARD COMPUTER STAT

ORGANISATION OF TESTS

Figure 3.

COMPILED

CENTRAL COMPUTER

(1) A reduction in the dwell time of each patient’sresults because in the selective analysis the testsrequested for each patient are completed before thetests on the next sample are started.

(2) New specimens can be added at any stage in theprocess without interfering with the work flow onthe analyser.

(3) Stat specimens similarly can be added at any timeand processing of the tests begins immediatelyafter the completion of the tests on the previousspecimen.

(4) Bi-directional interfacing provides, in the selectivemode, a facility which would allow for the recall ofprevious results for each patient with immediateviewing and analysis of any analytical changeswhich may have occurred.

There are disadvantages, such as the possibility ofreagent carry-over and reduced sample rate.

The next point to be discussed is internal quality control.There is a need to review the whole concept of internalcontrol. This is nowhere more obvious than in thesituation of the selective analyser. If the traditionalapproach to quality control is used, a very large numberofquality control specimens would have to be run. Therehas been an evolution in the use of quality control in theclinical laboratory (figure 4), first with the acceptance of

EVOLUTION OF QUALITY CONTROL

IrlPACT

STABILITY -’tIANUFACTURER’ SQUALITY CONTROL "

Figure 4.

NOT USED

AFTER CALIBRATORS

INTERSPERSED

bJESTGARD AND INTERPRETATION

tJHAT IS QUALITY CONTROL?

the need,, then the developments which led to moreeffective program design and techniques, following whichthere was better understanding and interpretation of theresults. However, the role played by quality control mustbe reconsidered in the light of advances such as thestability inherent in the new analytical systems and thecommitment to quality of manufacture by the industry.The Black Box allows the laboratory staff to present asample and receive an answer. If one considers thefollowing points, the question can be asked, why are thelaboratories using quality-control materials to check theperformance of closed analytical systems?

(1) Quality-control materials are used to check theperformance of the analytical systems.

(2) The quality control material does not give a trueindication of the pre-analytical errors because it isa control known to the operator and so consciouslyor subconsciously may be treated more carefully.

185


(3) The systems are largely operator independent,allowing a sample to be presented and an analy-tical result is produced.

(4) Some systems recalibrate every time a sample ispresented; and others have calibration which isstable for three or more months.

(5) The manufacturer applies a very stringent qualitycontrol programme ’in house’.

(6) The manufacturers have accepted the responsibil-ity for the quality of the analytical system.

(7) The analytical performance of the systems asshown by the use of quality-control material isacceptable.

(8) For some analytes quality-control materials havebeen shown to react differently to the patientsample.

The above question should be put because there is atendency among the staff of laboratories to adopt atraditional attitude to internal quality control, whichdoes not reflect the advances made in analytical tech-niques.

The manufacturer is in a position to display a consider-able amount of information with respect to the perfor-mance of various components of the analytical system.These are available through the service modes. Takingthis fact into account and coupling it with the extensiveeffort which is put into guaranteeing the quality of thereagent systems in use, one wonders if it would not bepossible to devise a quality assurance system for thelaboratory which is independent of the conventional useof quality control material. The on-board services checkscould be monitored and a warning displayed if there wasa change in performance of clinical significance.

The question of how analytical rejection criteria areestablished is the next point for discussion. In ourlaboratory a Kodak EK 700 is monitored for its perfor-mance and the analytical performance data for thequality-control material are used to determine therejection criteria by calculating the mean and standarddeviation. Using this method of determining the criteriato be used for acceptance or rejection ofanalytical batchesleads to the figures in table 1. Ifthese are compared to theperformance criteria in the literature they are narrow.Some examples of performance criteria are given also intable 1. The 10%, 20% and 50% refers to the perfor-mance of the laboratories in those percentile in theAustralian Chemical Pathology Quality Assurance Pro-gramme. The data listed under ’best’ refer to the most

stringent performance criteria among published work.The ’goal’ refers to performance criteria taking intoaccount intra- and inter-biological variance. The prin-ciple of establishing acceptable limits of analyticalperformance by calculating the mean and standarddeviation from the existing performance of the systemshould be questioned. As can be seen from table 1, theperformance of the Kodak EK 700 system is tight forsome analytes and rejection based upon those criteriamay not be sensible. There is a need to consider theclinical requirements. In addition, the frequency ofuse ofquality control materials should be reviewed. If one wasto look at an analyser which has been available for a

Table 1. Imprecision datafor a carrier bound analytical system CVas percentage.

Analyte 700 10% 20% 50% Best GoalSodium 0"79 0"5 0"6 0"9 0"9 0"4Pot. 1"26 0"8 1"0 1"6 1"5 2"2Ca 1"24 0"9 1"3 2"1 1"45 0"9Chlor. 1"07 0"8 1"0 "4 "0 1.1Glue. 1.05 1.4 1.9 3.0 2.7 2"2

Table 2. Open analytical systems.

ADVANTAGESGreater flexibilityWider range of reagentsResearch applicationsOften consumables cost lessRange of tests more extensive

DISADVANTAGESMore dependent on operator’s skillsManufacturer’s QC not availableRequires skills to troubleshoot

Table 3. Closed analytical system.

ADVANTAGESManufacturer Quality AssuranceTendency for operator independencePositive identification of reagents

DISADVANTAGESRoutine analytical toolOften consumables cost moreReliance on Manufacturer’s QAReliance on Manufacturers investigationsThe ’Black Box’Range of tests often restricted

number of years, the Technicon SMAC, the quality ofperformance as determined by the quality control pro-grammes on the system at the Institute of Medical andVeterinary Science is good and the results would indicatethat perhaps there is a need to review the internal qualitycontrol programme. Specimens are inserted in thefollowing sequence; recalibration step, two levels ofquality control material, 16 specimens, two levels ofquality control material, 8 specimens, two levels ofquality control material, recalibration step. As mentionedabove, the quality control data indicate that less stringentcontrol would be warranted. As a general statement, theprinciples of quality control are not reviewed oftenenough to ensure that the procedures for monitoring thequality of the analytical data are keeping abreast ofadvances in analytical techniques. The point to be madeis that with the introduction of new techniques and newanalytical systems the existing laboratory operationsshould be reviewed to ensure that they are not restrictingthe appropriate utilization of the system.

The final point to be covered in this section of thesymposium’s papers relates to the advantages anddisadvantages of open and closed analytical systemsoperating in the selective analysis mode. From the pointslisted in tables 2 and 3, it becomes clear that a decision

186


has to be made with respect to the role that the analyticalsystem is to play in the laboratory because open systemshave advantages ifoperated in a research or developmen-tal mode. The inherent flexibility of analysers whichoperate in the selective mode should be weighed againstthe possible decrease in the sample rate ofthe system if itis operated in this mode.

In conclusion, it is important that positive identification,bi-directional interfacing, selectivity and the value ofresident chemistries be understood, as these are facilitieswhich are integral to the effectiveness of the laboratoryorganization and should be considered carefully in thepurchase of analytical systems. In addition, there is aneed to review the design and operation of internalquality control programmes in light of the performancecharacteristics of the systems available to the laboratory.

Summary

Selective analysers have a significant impact on theorganization of the laboratory and there are areas where

the systems will continue to develop and extend the rangeof facilities available.

In this respect, positive identification, bi-directionalinterfacing and on-board interpretative programmes willplay a major role in extending the value to the laboratory.The stability of the analytical systems has led to aquestioning of the more traditional approach to qualitycontrol.

When seeking to obtain the optimum value from ananalytical system there is a need to affirm how. qualitycontrol is to be applied and to make greater use of thefacilities available in diagnostic and the service modes ofthese systems. The self-monitoring checks available in thevarious operating modes should be considered as a formof quality control.

Selective analysers need to be understood for the poten-tial of these systems to be fully utilized.

Reference1. Journal ofAutomatic Chemistry, 2, (1980).

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187

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