Upsala J Med Sci 91: 225-227, 1986 

Working Group for the Rational Use of Urinary Test Strips 
Anders Kallner, Rudolf Jagenburg, Bertel Berg and Kristoffer Hellsing 

Protocol f o r  the evaluation of reagent sets (Chemicals and fnstruments) 
with special reference to "SPOT-tests" 

The continuous development and marketing of new reagents and 
instruments makes it desirable to design a protocol which 
utilizes acceptable and well recognized methods. Such an app- 
roach is particularly important since many laboratories are 
faced with a demand to compare different reagent sets: It 
would be an advantage also if manufacturers would describe 
their products in these terms. The working group is in the 
process of finalazing a report on evaluation of test strips, 
highlighting also problems of discrimination values in binary 
and paucinary tests. 
The following provisonal protocol has been designed to esti- 
mate imprecision and inaccuracy from patient samples as well 
as from control and reference materials. Also, the with-in, 
between-series and total variation should be estimated. 
Special methods are advised for the estimation of linearity, 
and the effects of lipemia and hemolysis. Special attention 
should be given to the effect of the sample matrix. Several 
recommendation for evaluation of methods have been published 
with details on statistical treatment of the results (1-3). 

1. Imprecision and inaccuracy 

1.1. PATIENT SAMPLES 
About 36 samples should be determined in dupli- 
cates on three different occasions. The samples 
should also be analyzed with an agreeable, well 
controlled method which agrees as much as 
possible with a reference methodology. The 
patient samples should be of different concen- 
trations. 

1.1.1. 

1.1.2. 

Estimate the regression between the means of the 
duplicates and the values obtained by that used 
as a reference. 

Estimate the standad deviation from the results 
of the duplicate analyses of three levels, 
subnormal, "decision interval" and increased 
values. 

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1.1.3. 

1.2. 

1.2.1. 

1.2.2. 

Identify and reexamine all outliners. Evaluate 
deviation in view of matrix on systemic 
effects. 

REFERENCE MATERIAL 
Use three levels of concentrations of a refe- 
rence material which is as close as possible to 
human. The number of analyses on each level 
should be abut 25. 

Estimate the mean, standard deviation and 
coefficient of variation for each reference 
material. 

Use the reference material which is closest to 
the decision level and determine the concentra- 
tions in 15 different runs. Several runs may be 
carried out per day but they must then be 
initiated the normal way, including shut-down of 
the instrument, recalibration etc. In each run 5 
values should be determined. 

1.2.2.1. Calculate the average within-batch variation. 

1.2.2.2. Calculate the between-batch variation. 

1.2.2.3. Calculate the total variation. 

2. Testing other parameters of performance. 

2.1. HEMOLYSIS (addition of hemolysed erythrocytes). 
A hemolysate is prepared from washed human 
erythrocytes which are frozen and thawed several 
times. A series of dilution is made from this 
concentrate, using 0.15 mol/L NaCl as diluent. 
Suitable concentrations are 320, 160, 80, 40, 
20, 10 and 5 g/L. A serum sample is diluted 1:lO 
with the appropriate hemoglobin sample. These 
samples as well as a sample diluted with 0.15 
mol/L NaCL 1:lO are determined in duplicates. 

2.2. 

2.3. 

R LIPEMIA (addition of fat emulsion, Intralipid 
is provisionally suggested). 
The initial concentration of 100 g/L is diluted 
with 0.15 mol/L NaCl to concentrations of 100, 
50, 25, 12 and 6 g/L. A serum sample is then 
diluted 1:lO with these dilutions of the €at 
emulsion, including a zero sample. Samples 
should be analysed in duplicates. 

BILIRUBINEMIA. 
A similar test of the influence of bilirubin 
should be carried out. A suitable test material 
is still to be found. 

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2.4. 

2.5. 

2.6. 

2 . 7  

DRUGS. 
Drugs interfering with the methods chemically 
should be systematically tested. The booklet 
"Drug interference and effects in Clinical 
Chemistry" (Apoteksbolaget, Stockholm, Sweden) 
should be consulted. 

LINEARITY 
The linearity of the method should be tested 
over as wide a range as possible. Select a high 
and a low concentration serum and mix them in a 
suitable manner to obtain at least five points. 
Plot the found vs. the calculated results, if 
possible describe the performance using reg- 
ression analysis. 

SAMPLE VOLUME. 
Analytical results should be determined using 
from -10 to +lo% of the recommended volume of 
sample. 

ERYTHROCYTE, VOLUME FRACTION. 
In case whole blood is recommended the effect of 
varying the EVF should be considered within the 
fysiological range. 

It is understood that deviations from the outlined method 
could be necessary due to technical or other circumstances. 
Depending on the reagent set evaluated, other items might also 
be important to consider. 

Several reagent sets (chemicals and/or instruments) are in the 
process of being tested in accordance with this protocol. 

Extensive lists of further reference to the literature are 
fund in these papers. 

1. IFCC Expert Group on Diagnostic Kits and Reagents. 
a) Recommendations for specifications on Labelling of 

Clinical Laboratory Materials. 
b) Guidelines for the Evaluation of Clinical Chemistry Kits 

in IFCC Recommendations and Related Documents Volume I, 
1978-83 Walter De Gruyter 1984. ISBN 3-11-008766-9. 

2. IFCC/WHO Principles and Recommendations of Evaluation of 
Diagnostic Reagent Sets used in Health Laboratories with 
limited resources. J Clin Chem Clin Biochem (1984) 22: 817 
with appendicies A-E (Glucose, Urea, Total Bilirubin, Total 
Protein and Albumin). 

3 .  White GH and Fraser CG: The evaluation kit for clinical 
chemistry: a practical guide for the evaluation of methods, 
instruments and reagent kits. J Autom Chem (1984) 6 :  122. 

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