Collaborative study results

M. G., Stella, C., Veuthey, J.-L., Estevenon, O., Van Schepdael, A., Roets, E., and Hoog-martens, J. (2003), Determination of uncertainty in analytical measurements from collaborative study results on the analysis of a phenoxymethylpenicillin sample, Anal. Chim. Acta, 481, 261-272. 

Comparing these collaborative study results to the average expected from the Horwitz curve, a composite RSD, curve of more than 300 collaborative studies. For SFB the average Horwitz ratios were 0.8, 0.59 and 0.55 for the three spiking levels for PCD the ratios were 1.38, 0.33 and 0.96. Both SFB and PCD showed acceptable within and between laboratory precision. (The Horwitz ratio compares the RSD, at the various levels and in the various matrices of this method with those RSD, values predicted based historically on methods for a wide variety of analytes reported in AOAC collaborative studies a ratio <2 is considered to have acceptable and typical precision (12). 

As part of a collaborative study of a new method for determining the amount of total cholesterol in blood, two samples were sent to ten analysts with instructions to analyze each sample one time. The following results, in milligrams of total cholesterol per 100 mb of serum, were obtained... 

What is the estimated relative standard deviation for the results of a collaborative study in which the sample is pure analyte (100% w/w analyte) Repeat for the case in which the analyte s concentration is 0.1% w/w. 

Of course, equation 14.26 only provides an estimate of the variability in results submitted by those participating in a collaborative study. A relative standard deviation that is within one-half to twice the estimated value suggests that the method performs acceptably when used by analysts in different laboratories. The percent relative standard deviation for a single analyst should be one-half to two-thirds that for the variability between analysts. 

It is not strictly required to use the same attributes in each data set. This allows the comparison of independent QDA results obtained by different laboratories or development departments in collaborative studies. Also within a single panel, individual panellists may work with personal lists of attributes. When the sensory attributes are chosen freely by the individual panellist one speaks of Free Choice Profiling. When each panellist uses such a personal list of attributes, it is likely that... 

The third approach is also known as a collaborative study or a collaborative trial. Both names underpin the joint effort of the coordinator and participants to characterize the reference material. In any case, the measurement methods used in the characterization should be traceable to what is called stated references , and preferably to SI. The aspect of traceability of measurement results goes well beyond the actual measurements it also includes the transformation of the sample from the state of the reference material to the state in which it can be measured. An example of such a transformation is the destruction of the sample. 

In such a case, based on the results of a collaborative study, a content is assigned to the corresponding reference substance which is method specific, i.e. it is only to be used with the method described in the monograph. The establishment of these substances is described in more detail later in the Chapter. 

If samples are highly impure or decompose readily, then use of the UV method is inappropriate, and LC/MS has been shown to be the most suitable detection system under such conditions [15]. When used carefully, LC/MS produces excellent results however, when LC/MS data-taking is driven very rapidly (e.g., 20 min/ plate), disappointing results have been noted in collaborative studies (data not shown). 

The degree of validation of the methods may be quite different. What validation means is that the method has been subject to a study which shows that, as applied in the user s laboratory, it provides results which are fit for their intended purpose. The method satisfies some pre-defined criteria. When standard or internationally agreed methods are being developed, the validation of the method is more complicated and time-consuming than that of methods developed in-house. Such validation involves a collaborative study using analysts working in a number of laboratories. This has already been mentioned in Chapter 1 and the organization of collaborative studies is discussed in Chapter 7. However, this more elaborate procedure does not necessarily mean that the method is more reliable than in-house methods. 

The previous chapters of this book have discussed the many activities which laboratories undertake to help ensure the quality of the analytical results that are produced. There are many aspects of quality assurance and quality control that analysts carry out on a day-to-day basis to help them produce reliable results. Control charts are used to monitor method performance and identify when problems have arisen, and Certified Reference Materials are used to evaluate any bias in the results produced. These activities are sometimes referred to as internal quality control (IQC). In addition to all of these activities, it is extremely useful for laboratories to obtain an independent check of their performance and to be able to compare their performance with that of other laboratories carrying out similar types of analyses. This is achieved by taking part in interlaboratory studies. There are two main types of interlaboratory studies, namely proficiency testing (PT) schemes and collaborative studies (also known as collaborative trials). 

This chapter has considered two of the types of interlaboratory comparison exercise in which your laboratory may participate. It is important to remember that proficiency testing schemes and collaborative studies have different aims. The former is a test of the performance of the laboratory, whereas the latter is used to evaluate the performance of a particular analytical method. Laboratories should participate in proficiency testing schemes (where an appropriate scheme is available) as this provides an independent check of the laboratory s performance. This chapter has described the key features of proficiency testing schemes and explained how the results from participation in a scheme should be interpreted. 

Hautfenne A, Pocklington WD, Wolfe JP. 1987. Determination of hexane residues in oils Results of a collaborative study and the standardised method. Pure Appl Chem 59(11) 1561-1570. 

Parry, J.M., Arlett, C.F. and Ashby, J. (1985). An overview of the results of the in vivo and in vitro test systems used to assay the genotoxicity of BZD, DAT, DAB and CDA in the second UKEMS study. In Comparative Genetic Toxicology The Second UKEMS Collaborative Study, (Parry, J.M. and Arlett, C.F., Eds.). Macmillan, London, pp. 597-616. 

It is important to appreciate that the statistical significance of the results is wholly dependent on the quality of the data obtained from the trial. Data that contain obvious gross errors should be removed prior to statistical analysis. It is essential that participants inform the trial co-ordinator of any gross error that they know has occurred during the analysis and also if any deviation from the method as written has taken place. The statistical parameters calculated and the outlier tests performed are those used in the internationally agreed Protocol for the Design, Conduct and Interpretation of Collaborative Studies.14... 

H3. Highsmith, W. E., Chong, G. L., Orr, H. T., Perry, T. R., Shaid, D., Farber, R., Wagner, K., and Thibodeau, S. N., Frequency of the delta Phe508 mutation and correlation with XV.2c/KM-19 haplotypes in an American population of cystic fibrosis patients Results of a collaborative study. Clin. Chem. (Winston-Salem, NC) 36, 1741-1746 (1990). 

This work was carried out at Brookhaven National Laboratory under contract with the U. S. Department of Energy and supported by its Office of Basic Energy Sciences. We wish to acknowledge many valuable discussions with Prof. H. L. Friedman and Dr. B. L. Tembe and thank them for permission to refer to results of our collaborative study (12) prior to publication. We also wish to thank Dr. J. Logan for permission to use Figure 4, Dr. S. Ehrenson for supplying a computer program which was used in the ellipsoidal dielectric calculations, and Prof. N. R. Kestner for several helpful comments. 

Somatropin is a protein having the structure (191 amino acid residues) of the major component of growth hormone produced by the human pituitary. Somatropin is produced by a method based on recombinant DNA technology. Recently the results of a collaborative study between 14 laboratories have been reported, in which a new CE method was compared with the existing test for isoform distribution by isoelectric focusing. The CE method was found to be superior to the method of isoelectric focusing. As a result CE is applied for identification... 

N. et al. (2000) In vitro micronudeus assay with Chinese hamster V79 cells - results of a collaborative study with in situ exposure to 26 chemical substances. Mutation Research, 468, 137-163. 

However, very recent results obtained in a collaborative study by one of the authors eliminate this anomaly, and correct Table 1 and Fig. lb. Starting with the... 

Results of a National Institute of Mental Health collaborative study indicated that antidepressant therapy should not be discontinued before 4-5 symptom-free months have passed (Prien and Kupfer 1986). Most clinicians treat single episodes of depression for a minimum of 6 months. In most cases, antidepressant medication should be continued at the same dose that resulted in remission—hence the saying, what gets you well keeps you well. ... 

Grafe, A., I. E. Mattern, and M. Green, A European Collaborative Study of the Ames Assay. I. Results and General Interpretation, Mutat. Res., 85, 391-410 (1981). 

Data from several large collaborative studies were plotted, with results fitting the exponential model (for constant relapse rate) more accurately than a linear model. The relapse rates for these studies were as follows ... 

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