machine validation for clinical biochemistry analyzer...machine validation for clinical biochemistry...
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Machine Validation for Clinical Biochemistry Analyzer
Submitted 25 October 2016, Under Review
Lenon Scotch1, Allen Matubu
2, Danai Tavonga Zhou
1,3
1. University of Zimbabwe College of Health Sciences, Department of Medical Laboratory Sciences,
P.O. Box AV 178, Avondale, Harare, Zimbabwe
2. University of Zimbabwe, College of Health Sciences, Department of Medicine, P.O. Box AV 178,
Avondale, Harare, Zimbabwe
3. Africa University, Faculty of Health Sciences, Medical Laboratory Sciences, P. O Box 1320,
Mutare, Zimbabwe
Emails: [email protected], [email protected], [email protected], OR
ABSTRACT
Unreliable results issued by many laboratories have dire consequences such as unnecessary
treatment, treatment complications, failure to provide proper treatment, delay in correct
diagnosis and additional, unnecessary testing. Optimum operating conditions are difficult to
control in clinical laboratories and these negatively affect the function of clinical machines
and quality of laboratory results. Therefore validation is necessary to determine a machine’s
optimum operating conditions. Our cross-sectional study aimed to evaluate performance
specifications of a new department analyzer compared to those established by the
manufacturer before comparing the new machine’s performance to an old pre-validated
machine serving as the Gold Standard. Blood samples (N=173) were analyzed for glucose,
creatinine and urea, using the Gold Standard chemistry analyzer and the new machine
respectively. The results obtained were assessed for accuracy, linearity, carryover, reference
ranges, analytical measurable ranges, clinical reportable ranges, specificity and sensitivity to
determine validity of the new machine. From our results accuracy, linearity, carryover,
reference ranges, analytical measurable ranges, clinical reportable ranges, specificity and
sensitivity were all within manufacturers’ stated claims. Results were also comparable to the
Gold Standard machine.
Introduction
Background and literature review
Validation is the process of determining the performance characteristics of method or
procedure or process [1]. It is a prerequisite for judgment of the suitability of produced
analytical data for the intended use. This implies that a method may be valid in one situation
and invalid in another [2]. The process is intended to check that development and verification
procedures of an analyzer meet initial requirements, specifications, and regulations. It is a
process of establishing evidence that provides a high degree of assurance that the machine
accomplishes its intended requirements [1, 3]. Validation often involves acceptance of fitness
for purpose with end users and other product stakeholders.
Validation is important and can be used during accreditation of clinical laboratories and
certification, using common standards and practices. Regulatory agencies require that a
laboratory validate an instrument before it is put into use for patient testing [4, 5]. The
Clinical Laboratory Improvement Amendment (CLIA) regulations state that the laboratory
must demonstrate that it can obtain performance specifications comparable to those
established by the manufacturer when the laboratory introduces a new clinical chemistry
analyzer. Reliable data depends on a robust system design, which is initially validated by the
manufacturer using formal study procedures and subsequently verified by the end user
laboratory focusing on the laboratory’s specific patient populations [1, 2, 6].
Zimbabwe has established independent and internationally credible accreditation bodies
for example the Standards Association of Zimbabwe (SAZ). Standards are accomplished
through the establishment of a world-wide network of national accreditation bodies, which
will through Multilateral Agreements (MLAs) eventually; ensure that the competence of
certification bodies, inspection bodies and laboratories are assessed on the same principles,
regardless of their location. In Clinical Chemistry laboratories assessments are based on the
harmonized ISO standards for example ISO 15189 Certification for Medical Laboratories
[3,7].
From a medical perspective, the value of an automated clinical chemistry analyzer is to
provide physicians and other health care providers with reliable clinical data for patient
management. All results must be statistically and medically comparable on any clinical
chemistry analyzer [8, 9]. Before reporting patient test results, the laboratory needs to
demonstrate the accuracy and precision of its analyzer/s [6, 10].
Laboratory results influence 70%-75% of medical diagnosis hence quality of laboratory
service directly affects the quality of health care. Laboratory results must be as accurate as
possible, and laboratory operations must be reliable, and reporting must be timely in order to
be useful in a clinical or public health setting. If inaccurate results are provided, the
consequences can be very serious [11], for example, there may be unnecessary treatment,
treatment complications, failure to provide the proper treatment, delay in correct diagnosis
and additional and unnecessary diagnostic testing [9].
We carried out a validation procedure for a new machine at the University of Zimbabwe,
College of Health Sciences, in the Department of Medical Laboratory Sciences. The
validation involved a comparison between two machines: an old machine which we refer to
as the Gold Standard and a new machine. The aim of this report is to avail information to
other laboratories about the practical aspects of machine validation and share results of a
validation process in our setting. Literature on validation processes in clinical chemistry
laboratories in our setting is very scarce.
Materials and Methods
Laboratory Methods
The procedure focused firstly on the laboratory’s own procedures using the new analyzer.
During this process, measurements of common chemistry analytes such as: glucose,
creatinine and urea were performed. This was to ensure that the equipment was operating
within established parameters, giving reproducible results that meet pre-determined
specifications [12]. The validation procedure also verified the reportable range of test results
for the new machine’s test system and showed whether manufacturer's reference intervals are
appropriate for our laboratory's patient population [13, 14].
Accuracy Testing
In order to verify accuracy: glucose, creatinine and urea levels of 173 serum specimens were
determined using the new analyzer. Results, obtained using the new analyzer were compared
with the manufacturer’s insert details of accuracy determination [10]. Standard deviation and
coefficient of variance had to meet manufacturer’s stated claims [5]. Results were then
compared with those obtained from the Gold Standard chemistry analyzer. Standard deviation
and coefficient of variances were used to compare the two machines [5, 9, 10]. Limits of
acceptability for glucose, creatinine and urea levels for new analyzer were set by the
Laboratory Quality Assurance Department [4, 5, 10].
Precision
Glucose, creatinine and urea levels of multi sera controls were determined using the new
chemistry analyzer. Coefficient of variances were determined and used to assess the precision
of the machine [4]. Within run and between run reproducibility were determined by running
the negative pathological controls and normal controls as follows: For within run, 20
replicates of pathological control and 20 replicates positive control were tested in one run
each. For between run reproducibility, both pathological and normal controls were tested 5
times per day for 4 days to obtain a total of 20 replicates each [6, 9].
For the between run and within run precision, the results from the normal and pathological
controls were used to calculate the coefficient of variance (CV). The CV obtained was
compared to the manufacturer’s CV. The laboratory CV had to be less than or equal to the
manufacturer’s stated CV [4, 6, 10].
Linearity Testing
Glucose, creatinine and urea levels of five (5) serum specimens for each parameter were
determined using Gold Standard analyzer and new chemistry analyzer respectively to assess
the linearity of the machine. When plotted, the values had to be equidistant from each other
[16, 17, 18]. Six specimens were tested three (3) times each for each parameter and the data
was plotted immediately to identify and correct any outliers [18]. Data was plotted in
regression analysis program. The Linearity spreadsheet performed all necessary calculations
[18]. Mean values from the Gold standard were plotted on the X-axis [17, 18]. Mean values
for the new analyzer were plotted on the Y-axis [18]. The slope and intercept were calculated
using linear regression. This can also be done using the Excel slope and intercept functions
[17]. Using slope and intercept, a predicted Y value complementary to each X value was
calculated [18]. The predicted Y values were plotted versus the corresponding known X
values on the same graph. A straight line was drawn to connect all the predicted Y points on
the graph [18]. Each measured Y value was subtracted from the associated predicted Y value.
The difference is the systematic error due to non-linearity [18]. Systematic errors were then
compared to 50% of the total error. Systematic errors had to be less than 50% of the total
error [17] to prove validity of the new machine.
Analytical Measurable Range (AMR)
Multi Sera control samples from linearity procedure were used [9, 13]. The lowest glucose,
urea and creatinine levels of the control sample were diluted to verify the low end of
Analytical Measurement Range (AMR) [13]. The highest sample values for glucose, urea and
creatinine levels obtained from linearity were used as the high end of the AMR [9]. Five
samples were run each in duplicate and the results averaged [14]. Data was evaluated
immediately to identify and correct any problems [9]. The reportable range had to lie within
the manufacturer’s Analytical Measurable Range (AMR) [9, 14]. The manufacturer’s upper
limit was accepted if the known sample was within the percent Total Allowable Error (TEa)
of laboratory’s AMR upper limit [9]. Measured values also had to be within TEa of the Gold
Standard machine values [8, 14]. The manufacturer’s lower limit could be accepted if the
known sample was within the minimum detectable difference or percent TEa of the lower
limit [8]. Measured values also had to be within TEa of the Gold Standard machine values
[8].
Clinical Measurable Range (CRR)
Four dilutions were made to cover the clinical measurable range, since minimum amount of
dilution was ideal and since accuracy decreases with increasing dilution [8, 14]. The
maximum value of dilution allowed could not exceed the manufacturer’s recommendations
for dilution [14]. Any sample that did not give a numerical value beyond this allowed
dilution is reported as greater than the upper end of the CRR [8]. A sample (H) with a very
high concentration of the analyte and a sample (L) with a very low concentration were
chosen. Eleven replicates of the low sample and ten replicates of the high sample were run in
the following order and no other sample could be run within the series
L1/L2/L3/H1/H2/L4/H3/H4/L5/L6/L7/L8/H5/H6/L9/H7/H8/L10/H9/H10/L11. A passing
status was given if carryover was less than the error limit which was based upon three times
the low-low SD [4, 8]. The manufacturer’s stated sensitivity was used.
Reference Ranges
To verify or transfer a published range, the 20 specimens for glucose, creatinine and urea
with normal values were analyzed. Ranges were determined using a non-parametric statistical
method to determine the 95% reference limits. The lower and upper reference limits were
defined as the 2.5th
and 97.5th
percentiles, respectively [13, 14].
Chemistry Analyzer operations
The new analyzer was run according to manufacturer’s instructions found in its operating
manual. Parameters were selected and tested for validation purposes, for example: urea,
creatinine and glucose. These parameters have the most diagnostic value and can be
confirmed using the manufacturers’ co-efficient of variances (CVs).
Study Design and Ethical Considerations
The cross sectional analytical study was carried out on 173 samples although minimum
sample size for validation is as low as 20. We hoped to improve power of study and therefore
the generalizability of our results to other laboratories in our setting. Blood samples in plain
tubes and fluoride tubes were used. Permission to carry out the proposed project was sought
from relevant authorities whilst ethical clearance was sought from the Joint Research Ethics
Committee of the University of Zimbabwe, College of Health Sciences and Parirenyatwa
Group of Hospitals (JREC).
Laboratory Processing and Analysis
Blood samples in plain and fluoride tubes were de-identified for confidentiality and assigned
numerical identifiers. Samples were centrifuged at 3000 revolutions per minute (rpm) for five
minutes and serum and plasma were aspirated using a micropipette. The serum and plasma
were aliquoted into serum pots and stored in a refrigerator at 2 -8 OC. Samples were thawed
at room temperature on the day of assaying. Samples were assayed on the new chemistry
analyzer and Gold Standard chemistry analyzer and results compared.
Results
Precision
The within-run precision and between-day precision results showed that the CVs for urea,
glucose and creatinine on normal and pathological control samples were within
manufacturer’s stated values (Tables 1 and 2 and Figs 1 and 2).
Table 1: Within-run Precision for New Analyzer
Analyte
Expected Results Observed Results
Acceptability
Within- run
Mfg’s
Precision
25% of
CLIA
Normal Control
CV%
Control Path
CV%
Urea 1% 2.25% 0.07% 0.04% Acceptable
Creatinine 10% 3.75% 0.03% 0.02% Acceptable
Glucose 1% 2.50% 0.04% 0.02% Acceptable
Table 2: Between-day Precision for New Analyzer
Analyte
Expected Results Observed Results
Acceptability Between-day
Mfg’s
Precision
33% of
CLIA
Normal
Control
CV%
Control Path
CV%
Urea 1% 2.97% 0.16% 0.02% Acceptable
Creatinine 10% 4.95% 0.002% 0.053% Acceptable
Glucose 1% 3.3% 0.31% 0.122% Acceptable
Figure 1: Correlation of glucose results between new and gold standard analyzer
(Accuracy)
Figure 2: Correlation of creatinine results between new and gold standard analyzer
(Accuracy)
Accuracy
Results for the measurement of glucose, creatinine and urea on the new analyzer were
accurate based on the Coefficient of Variance and Standard Deviation (SD) obtained for these
analytes (Fig 3). Results were within manufacturer’s claims (Table 3, 4) and were accepted
on the basis of Total Allowable Error (TEa) values for urea, glucose and creatinine (Table 5).
Table 3: Accuracy-1 for New Analyzer
Analyte
Total
Allowable
Error
Correlation
Coefficient
(R)
Linear
Regression
Statistics
Error Index
Range
% of
Error
Indices
-1.0 to 1.0 Acceptability
Expected
>0.975 Slope Intercept
Expected
-1.0 to1.0
Expected
≥ 95%
Urea 0.714mmol/
l or 9%
0.999 0.990 -0.128 -0.94-0.84 95% Acceptable
Creatinine 26.52umol/l
or 26.52%
0.997 0.970 1.724 -0.15-0.19 95% Acceptable
Glucose 0.33mmol/l
or 10%
1.000 1.002 -0.038 -0.34-0.21 95% Acceptable
Table 4: Accuracy-2 for New Analyzer
Analyte
Total
Allowable
Error
Correlation
Coefficient
(R)
MDP Error Index Range
Worst
Sigma
Metric Acceptabilit
y
Expected
>0.975
Expected
-1.0 to1.0
100% of
Error
Indices:
-1.0 to 1.0
Expected
:
>2.0
Urea 0.714mmol/
lor 9%
0.999 -0.3-0.2 yes 15.2 Acceptable
Creatinin
e
26.52umol/l
or 15%
0.997 -0.319-0.1 yes 65.7 Acceptable
Glucose 0.33mmol/l
or 10%
1.000 -0.017-
0.0428
yes 19.7 Acceptable
Table 5: Table of Total Allowable Error Recommended for Validation requirements:
Minimum Recommended Validation requirements for Chemistry Total Allowable
Error (TEa) for Some Common Analytes (http://www.dgrhoads.com/db2004/ae2004.php)
Analyte
Total Error Limits (whichever is greater)
(whichever is greater) Precision
Percentage Minimum detectable
difference or absolute value
Short Term
25% TE
Long Term
33% TE
Albumin ± 10% (1) ±0.2 g/dL, 2.0 g/L (4) 2.5% 3.3%
Alk. Phos ± 30% (1) ±5.0 U/L (4) 7.5% 9.9%
ALT ± 20% (1) ±5.0 U/L (4) 5.0% 6.6%
Amylase ± 30% (1) ±5.0 U/L (4) 7.5% 9.9%
AST ± 20% (1) ±5.0 U/L (4) 5.0% 6.6%
Bilirubin, Direct ± 20% (2) ± 0.4 mg/dL , 6.84 umol/L (2) 5.0% 6.6%
Bilirubin, Total ± 20% (1) ± 0.4 mg/dL, 6.84 umol/L (1) 5.0% 6.6%
Calcium ± 8.3% (4) ± 1.0 mg/dL, 0.25 mmol/L (1) 2.08% 2.74%
Chloride ± 5% (1) ±2.0 mmol/L (4) 1.25% 1.65%
Cholesterol ± 10% (1) ±3.0 mg/dL, 0.08 mmol/L (4) 2.50% 3.3%
Creatinine ± 15% (1) ± 0.3 mg/dL, 26.52 µmol/L (1) 3.75% 4.95%
Creatine Kinase ± 30% (1) ±5.0 U/L (4) 7.5% 9.9%
Glucose (serum/
CSF) ± 10% (1) ± 6.0 mg/dL, 0.33 mmol/L (1) 2.50% 3.3%
HDL Cholesterol ± 30% (1) ± 2.0 mg/dL, 0.05 mmol/L (4) 7.5% 9.9%
Lactate ± 10% (9) ± 0.2 mmol/L (9) 2.5% 3.3%
Lactate
Dehydrogenase ± 20% (1) ±5.0 U/L (4) 5.0% 6.6%
LDL-Chol. Calc ± 30% (5) Not available 7.5% 9.9%
LDL-Chol. Meas. ± 30% (2) Not available 7.5% 9.9%
Lipase ± 30% (2) ±8.0 U/L (4) 7.5% 9.9%
Magnesium ±25% (1) ±0.2 mg/dL, 0.08 mmol/L (4) 6.25% 8.25%
Phosphorus ±10.7% (2) ± 0.3 mg/dL, 0.097 mmol/L (2) 2.68% 3.53%
Potassium ± 12.3%* (4) ± 0.5 mmol/L (1) 3.08% 4.06%
Protein, Total
(Serum) ±10% (1) ± 0.2 g/dL, 2.0 g/L (4) 2.5% 3.3%
Protein, Total
(CSF) ±20% (11) Not available 5.0% 6.6%
Sodium ± 3.1%* (4) ± 4.0 mmol/L (1) 0.78% 1.32%
Transferrin ±20% (2) ±5.0 mg/dL, 0.05 g/L (7) 5.0% 6.6%
Triglycerides ±25% (1) ±4.0 mg/dL, 0.05 mmol/L (4) 6.25% 8.25%
Urea (BUN) ±9% (1) ± 2.0 mg N/dL, 0.714 mmol/L
1) 2.25% 2.97%
Uric Acid ±17% (1) ±0.5 mg/dL, 30 µmol/L (4) 4.25% 5.61%
Vitamin B-12 ± 30% (6) ±30 pg/mL, 22.2 pmol/L (6) 7.5% 9.9%
Linearity results
The linearity results obtained for urea, glucose and creatinine were acceptable (Figs 4, 5 and
6) implying that there was no significant difference in the performance of the Gold Standard
and new analyzer (Table 6)
Figure 3: Correlation of urea results between new and gold standard analyzer for
accuracy
Figure 4: New analyzer glucose linearity scatter plot
Figure 5: New analyzer creatinine linearity scatter plot
Table 6: Linearity for New Analyzer
Analyte
Linear Regression
Statistics
Allowable
Systematic Error Linear Range
Verified Evaluation
Slope Intercept 50% of TEa
Urea 0.059 -2.901 7.5 1.2-39.3 mmol/l Linear
Creatinine 1.623 -110.619 4.5% 10-1062 umol/l Linear
Glucose 0.044 -2.272 5% 0.6-31.57 mmol/l Linear
Analytical Measurable Range (AMR) and Clinical Reportable Range (CRR)
The AMR and CRR for urea, glucose and creatinine were within manufacturer’s AMR ranges
and within reportable ranges. For CRR after 1:10 dilution the lower and upper limits on
verified values obtained and the ranges had were the same as AMR and reportable range
(Table 7, Graph 6).
Expected Urea Concentration (mmol/L)
Table 7: Analytical Measurable Range (AMR) and Clinical Reportable Range (CRR)
for New Analyzer
Analyte Mfg’s
AMR
Low
Value
Verified
High
Value
Verified
Reportable
Range Dilutions CRR
DAIDS
Toxicity
Grade 4
Urea 1-40
mmol/L
7.5 8.63 1-40 1:10 1-40 Requires
dialysis
Creatinine 9-2420
umol/L
96.6 130 9-2420 1:10 9-2420 3.5xULN
Glucose 0.3-28
mmol/L
4.1 6.03 0.3-28 1:10 0.3-28 >27.75
Figure 6: New analyzer urea linearity scatter plot
Carryover
Carryover results obtained for urea, glucose and creatinine were less than the error limit of
three times low-low standard deviation (Table 8).
Table 8: Carryover for New Analyzer
Analyte Low-
low
Mean
High-
low
Mean
Low-low
Standard
deviation
High-low
Standard
deviation
Error
limit
Carryover Status
Urea 7.58 7.68 0.045 0.110 0.134 0.1 Pass
Creatinine 91.68 91.8 0.045 0.071 0.134 0.12 Pass
Glucose 2.706 2.722 0.005 0.008 0.016 0.016 Pass
Expected Urea Concentration (mmol/L)
Sensitivity and Specificity
Sensitivity and Specificity results were adopted from the manufacturer’s instrument package
inserts (Table 9). Interference substances such as: icterus, haemolysis, lipemia, ascorbic acid
and bilirubin were assumed to have no significant effects on glucose, creatinine and urea
levels.
Table 9: Summary of manufacturer’s claims on Specificity and Sensitivity for New
Analyzer
Analyte
Specificity (Interfering Substances) Sensitivity Confidence
Urea Icterus – No significant effect
Hemolysis – No significant effect
Lipemia – No significant effect; >Abs flagging may
occur
Ascorbic acid- No significant effect
Billirubin- No significant effect
1 mmol/L 99.7%
Creatinine Icterus – No significant effect
Hemolysis – No significant effect
Lipemia – No significant effect; >Abs flagging may
occur
Ascorbic acid- No significant effect
Billirubin- No significant effect
9 umol/L 99.7%
Glucose
Icterus –No significant effect
Hemolysis- No significant effect
Lipemia- No significant effect
Ascorbic acid- No significant effect
Billirubin- No significant effect
0.3
mmol//L
99.7%
Reference ranges
The reference ranges; results obtained on established patients’ reference ranges had to be
comparable with manufacturer’s reference ranges. Verified ranges for urea and glucose were
within manufactures’ stated ranges (Table 10).
Table 10: Reference ranges for New Analyzer
Analyte
Mfg’s
reference
range
Reference range
cited
Verified
reference
Range
Established
patients reference
range
%verified
expected
(>/= 90%
Urea
6.38-8.63
mmol/L
Mfg’s reference
range
7.5-8.63
mmol/L
2-62.5 mmol/L 100%
Creatinine
77.9-105.3
ummol/L
Mfg’s
Reference
ranges
96.6-130
ummol/L
33-1726 ummol/L 85%
Glucose
3.9-6.4
mmol/L
Mfg’s reference
range
4.1-6.03
mmol/L
4.1-6.4 mmol/L 100%
Discussion
Validation aims to establish evidence that provides a high degree of assurance that the
machine accomplishes its intended requirements [1, 3, 15]. Overall results for all parameters
measured were within the manufactures’ stated claims. The within-run precision and
between-day precision results agreed with manufacturer’s stated Coefficient of Variances
(CVs) for urea, glucose and creatinine on normal and pathological control samples (Tables 1
and 2). The Coefficient of Variance (CV) and Standard Deviation (SD) for urea, glucose and
creatinine fell within defined Total Allowable Error (TEa). TEa values were calculated values
adopted from minimum recommended validation requirements for chemistry Total Allowable
Error (Tea) listed in Table 5 [8, 9, 16]
The measurement of glucose, creatine and urea with new analyzer was accurate based on
the correlation coefficient (CV) and Standard Deviation (SD) obtained for these analytes. CV
and SD had to be within manufacturer’s claims (Table 3), and were acceptable on the basis of
Total Allowable Error (TEa) values for urea, glucose and creatinine (Table 5). Error indices
and % error index lay within expected range (Table 3). Medical Decision Point (MDP) error
index ranges were acceptable and the 100% error indices fell within the manufactures’ stated
claims.
The linearity results obtained for urea, glucose and creatinine were also acceptable (Figs 4,
5 and 6). i.e. there was no significant difference in the performance of the Gold Standard and
new analyzer (Table 6). Systemic errors had to fall within acceptable limits and meet
manufacturer’s stated claims in order to show that a machine’s status or capacity correlates
with that of the Gold Standard analyzer. The systemic error were less than 50% total error
because validation protocols states that the systemic error of the machine being validated
should be less than 50% total error for it to pass the validation [17]. There was no significant
difference between the results produced by the new analyzer and those produced by the Gold
Standard Analyzer in our study.
The Analytical Measurable Ranges and Clinical Reportable Ranges (AMR and CRR) for
urea, glucose and creatinine had to be within manufacturer’s AMR ranges and within
reportable ranges. For CRR after 1:10 dilution the lower and upper limits on verified values
was the same as AMR and reportable range (Table 7, to show that the new machine is reliable
[13]. Carryover results obtained for urea, glucose and creatinine fell below the error limit of
three times low-low standard deviation (Table 8) suggesting that the machine’s error is within
expected range and that its error was insignificant.
Sensitivity and Specificity results were adopted from the manufacturer’s instrument
package inserts. Interference substances such as icterus, haemolysis, lipemia, ascorbic acid
and bilirubin were assumed to have no significant effects on glucose, creatinine and urea
(Table 9). Reference ranges results obtained on established patients’ reference ranges were
either lower or higher than manufacturer’s reference ranges due to different environmental
and operating conditions. Verified ranges for urea and glucose were within manufactures’
stated ranges and creatinine higher upper limit and lower limit were within manufacturers’
range (Table 10).
Conclusion
The validation results for the new analyzer showed that machine’s accuracy, precision,
carryover and verified reference ranges were within the manufacturer’s stated claims. The
machine produced results that were more or less comparable to those of the Gold Standard
analyzer. We could safely conclude that the new machine produces acceptable, comparable
results for patient management. Therefore the manufacturer’s claims were proved to be true
under the environment which assessments were made.
Limitations
The greatest challenge encountered during the study was the unavailability of literature from
other validation studies because validation reports are deemed private and confidential hence
they cannot be published. The manufacturer’s claims were the only available information for
comparison.
Recommendations for future
This paper will allow fellow clinical scientists in our setting to validate their analyzers using
tried and tested methods that are not too costly and can be carried out with minimal human
and chemical resources. Sharing of further information as published papers is also one way to
share skils and knowledge necessary to carry out this vital pre-analytical quality assurance
exercise.
Acknowledgements
1. University of Zimbabwe, College of Health Sciences, Department of Medical Laboratory
Sciences, academic and technical staff for assistance with the practical work
2. University of Zimbabwe, College of Health Sciences, Department of Community Medicine
for study design and statistical analyses
3. Parirenyatwa Group of Hospitals, Department of Clinical Chemistry for technical
assistance
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