Comparison of procedures for evaluating laboratory performance in external quality assessment schemes for lead in blood and aluminum in serum demonstrates the need for common quality specifications.
BACKGROUND
The different scoring methods used by eight European External Quality Assessment Schemes (EQASs) for occupational and environmental laboratory medicine were compared to develop suitable quality specifications as a step toward harmonization.


METHODS
Real results for blood lead and serum aluminum assays, reported by participants in Italian and United Kingdom EQASs, were evaluated according to individual scheme scoring criteria. The same results were then used to produce z scores using scheme-based between-laboratory SDs as the estimate of variability to determine whether simple performance-derived quality specifications produced better agreement among schemes.


RESULTS
The schemes gave conflicting assessments of participants' performance, and participants judged to be successful by one scheme could be defined as performing inadequately by another. An approach proposed by Kenny et al. (Scand J Clin Lab Invest 1999;59:585), which uses clinical inputs to set targets for analytical imprecision, bias, and total error allowable, was then used to elaborate quality specifications.


CONCLUSIONS
We suggest that the CLIA '88 recommendations for blood lead (+/- 40 micro g/L or +/- 10% of the target concentration, whichever is the greater) could be used as a quality specification, although a revision to +/- 30 micro g/L or +/- 10% is recommended. For serum aluminum, a suitable quality specification of +/- 5 micro g/L or +/- 20% of the target concentration, whichever is the greater, is suggested. These specifications may be used to compare laboratory performance across schemes.
Taylor
Andrew
A
Centre for Clinical Science and Measurement, School of Biomedical and Life Sciences, University of Surrey, Guilford GU2 7XH, United Kingdom. A.Taylor@surrey.ac.uk
Angerer
Jurgen
J
Claeys
Francoise
F
Kristiansen
Jesper
J
Mazarrasa
Olav
O
Menditto
Antonio
A
Patriarca
Marina
M
Pineau
Alain
A
Schoeters
Ilse
I
Sykes
Christophe
C
Valkonen
Sinikka
S
Weykamp
Cas
C
D000535:Aluminum / Q000097:blood*; D019411:Clinical Laboratory Techniques / Q000592:standards*; D004785:Environmental Pollutants / Q000097:blood* / Q000592:standards; D005062:European Union; D006801:Humans; D007854:Lead / Q000097:blood*; D016273:Occupational Exposure; D011786:Quality Control; D012016:Reference Values
D004785:Environmental Pollutants; D007854:Lead; D000535:Aluminum