Discrepancy of the international normalized ratio observed in the external quality assessment survey: a cause for concern

Abstract We investigated the ability of current immunometric methods for thyrotropin (TSH; thyroid-stimulating hormone) to distinguish between low-normal and subnormal hormone concentrations by using the data from an external quality assessment (EQA) survey in 1990. We computed the interassay (between-run) precision profiles from results from 101 laboratories, which used the five most popular kits in the survey; during the control period (one year) each laboratory assayed 4 EQA pools distributed (as hidden replicates) in five occasions. The interassay CV was relatively low (9-13%) for three pools in the normal TSH range (greater than 0.8 milli-int. unit/L) but markedly higher (30-40%, except for one more precise kit) in the subnormal range (0.2 milli-int. unit/L). We calculated the effect of the between-run variability on the diagnostic accuracy (discrimination between normal and subnormal values) for three representative TSH concentrations: 0.2, 0.4, and 0.5 milli-int. unit/L (0.3 milli-int. unit/L was considered the lower normal limit). The three concentrations were reasonably discriminated (P less than or equal to 5%), and only one kit showed a between-run CV less than 18% at 0.2 milli-int. unit/L. For the other four less-precise kits, only the higher TSH value (0.5 milli-int. unit/L) could be classified with an acceptable diagnostic reliability. With the most precise kit, one can distinguish two TSH concentrations in the 0.3-0.5 milli-int. unit/L range that differ by at least 30%; with the other kits, differences greater than 50-60% are needed for reliable discrimination. Thus many laboratories fail to achieve the functional sensitivity of a second-generation assay, even if they use immunometric methods. TSH assays with a better interassay precision in the low concentration range are needed.

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Evaluation of radioimmunoassay performance for staphylococcal enterotoxin in foods: application of external quality assessment survey

Canadian Journal of Microbiology ◽

10.1139/m86-111 ◽

1986 ◽

Vol 32 (7) ◽

pp. 602-604 ◽

Cited By ~ 1

Author(s):

N. Dickie ◽

K. Rayman ◽

M. Akhtar ◽

R. Foster ◽

M.-A. Gardiner ◽

...

Keyword(s):

Quality Assessment ◽

External Quality Assessment ◽

Collaborative Study ◽

Staphylococcal Enterotoxin ◽

Staphylococcal Enterotoxin A ◽

External Quality ◽

Assessment Survey ◽

The Given

An external quality assessment survey for staphylococcal enterotoxin A, B, and C2 determinations was performed in the collaborative study. Three analysts in two laboratories took part. Three types of food, cheese, salami, and pasta, were artificially contaminated with either one toxin only or all three toxins. A total of 378 analyses were performed. The group mean of the analytical values corresponded fairly well to the given enterotoxin concentrations. However, a considerable interlaboratory imprecision was found despite analyses being performed with the same reagents and methodology.

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Preparation of Control Blood for External Quality Assessment of Point-of-Care International Normalized Ratio Testing in the Netherlands

American Journal of Clinical Pathology ◽

10.1309/ajcp4aascg1nhqhx ◽

2014 ◽

Vol 141 (6) ◽

pp. 878-883 ◽

Cited By ~ 2

Author(s):

Anton M. H. P. van den Besselaar ◽

Charmane F. Abdoel ◽

Davina Ardanary ◽

Gert van de Kamp ◽

Fanny A. C. Versluijs

Keyword(s):

The Netherlands ◽

Quality Assessment ◽

External Quality Assessment ◽

Point Of Care ◽

International Normalized Ratio ◽

External Quality

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Use of Lyophilized Calibration Plasmas and Control Blood for International Normalized Ratio Calculation in External Quality Assessment of the Prothrombin Time

American Journal of Clinical Pathology ◽

10.1093/ajcp/102.1.123 ◽

1994 ◽

Vol 102 (1) ◽

pp. 123-127 ◽

Cited By ~ 9

Author(s):

Antonius M.H.P. ◽

Van Den Besselaar

Keyword(s):

Quality Assessment ◽

Prothrombin Time ◽

External Quality Assessment ◽

International Normalized Ratio ◽

External Quality ◽

Ratio Calculation ◽

And Control

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Pilot External Quality Assessment Survey for Post-Market Vigilance of In Vitro Diagnostic Medical Devices and Investigation of Trueness of Participants' Results

Clinical Chemistry and Laboratory Medicine (CCLM) ◽

10.1515/cclm.2003.030 ◽

2003 ◽

Vol 41 (2) ◽

Cited By ~ 11

Author(s):

Linda M. Thienpont ◽

Dietmar Stöckl ◽

Josef Kratochvíla ◽

Bedrich Friedecký ◽

Marek Budina

Keyword(s):

Quality Assessment ◽

Medical Devices ◽

External Quality Assessment ◽

External Quality ◽

Post Market ◽

In Vitro Diagnostic ◽

Assessment Survey

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External Quality Assessment of Point-of-Care Methods: Model For Combined Assessment of Method Bias and Single-Participant Performance by the Use of Native Patient Samples and Noncommutable Control Materials

Clinical Chemistry ◽

10.1373/clinchem.2012.191957 ◽

2013 ◽

Vol 59 (2) ◽

pp. 363-371 ◽

Cited By ~ 15

Author(s):

Anne Stavelin ◽

Per Hyltoft Petersen ◽

Una Ø Sølvik ◽

Sverre Sandberg

Keyword(s):

Quality Assessment ◽

External Quality Assessment ◽

Point Of Care ◽

International Normalized Ratio ◽

Comparison Method ◽

Case Scenario ◽

External Quality ◽

Target Values ◽

Quality Specifications ◽

Method Bias

BACKGROUND An important objective in external quality assessment (EQA) is to evaluate systematic deviations between methods. However, this is not possible when noncommutable control materials are used. The aim of this study was to develop an EQA model that incorporates a method bias evaluation using native patient samples into EQA schemes in which noncommutable materials are used. METHODS The model was applied twice in a point-of-care (POC) international normalized ratio survey among 1341 and 1578 participants. To estimate bias, about 100 native patient samples for each POC method were analyzed by a selected group of “expert” primary healthcare centers and on a designated comparison method. In addition, the expert centers as well as all the other EQA participants analyzed 2 noncommutable control materials, and method-specific target values were established. Both method bias and the deviation of a single-participant result from the method target value were evaluated against analytical quality specifications, making combined assessment possible. The best-case scenario occurred when both results were within the quality specifications. RESULTS Two POC methods fulfilled the quality specification for bias, whereas one did not. The best-case scenario was achieved by more than 90% of the participants using the methods with no bias, whereas none of the participants using the method with unacceptable bias achieved this result. CONCLUSIONS We propose an EQA model for which the bias of POC methods can be evaluated in situations in which commutable control materials are not available.

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Improvement of Coagulation Laboratory Practice in Thailand: The First-Year Experience of the National External Quality Assessment Scheme for Blood Coagulation

Archives of Pathology & Laboratory Medicine ◽

10.5858/133.1.72 ◽

2009 ◽

Vol 133 (1) ◽

pp. 72-77

Author(s):

Panutsaya Tientadakul ◽

Nisarat Opartkiattikul ◽

Wanida Wongtiraporn

Keyword(s):

Quality Assessment ◽

Blood Coagulation ◽

Coefficient Of Variation ◽

Partial Thromboplastin Time ◽

External Quality Assessment ◽

International Normalized Ratio ◽

Activated Partial Thromboplastin Time ◽

Laboratory Practice ◽

External Quality ◽

External Quality Assessment Scheme

Abstract Context.—In Thailand until 2005 there had been no external quality assessment scheme at the national level for blood coagulation tests. Only a few laboratories had an external quality assessment for these tests. In the year 2005, the Thailand National External Quality Assessment Scheme for Blood Coagulation was founded. Objectives.—To describe the establishment of the Thailand National External Quality Assessment Scheme for Blood Coagulation (including problems encountered and solutions), its progression and expansion, and the improvement of coagulation laboratory practice in Thailand during 2 trial surveys and 4 formal surveys conducted in the first 1;h1 years. Design.—Between 2005 and 2006, the external quality assessment samples for prothrombin time/international normalized ratio and activated partial thromboplastin time were distributed to the participants as well as the instructions and suggestions for the improvement of laboratory practice. From the data collected, the all-method coefficient of variation of the international normalized ratio and activated partial thromboplastin time was calculated for each survey. Results.—The number of participants increased during the first 1;h1 years that the surveys were conducted, from 109 to 127. Survey data demonstrate an improvement in response rate and an increase in the number of laboratories that determine their own reference ranges and repeat this for every change of reagent lot, using the appropriate anticoagulant. The increased precision of tests is indicated by the decrease of the all-method coefficient of variation of the international normalized ratio and activated partial thromboplastin time. Examples of individual laboratory improvement through feedback are also described. Conclusions.—The improvement of coagulation laboratory practice both through the instructions provided and liaison with participants was observed during the course of this scheme.

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