Inter-study comparisons

During the past 30 years numerous studies have assessed the potential role of vitamin C in the treatment or prevention of the common cold. During this time, articles have been published which both support [61-64], and refute [65-68] any positive benefit for vitamin C in the common cold. These differences arise mainly from the fact that investigators have employed different study protocols, which makes inter-study comparisons difficult. Moreover, the use of vitamin C had become an emotive issue and this has led to the publication of a number of articles with considerable bias (both for and against) its use as a treatment for the common cold. However, careful retrospective analysis of these data indicates that supplementation with gram amounts of vitamin C may indeed decrease the severity of cold symptoms, although the incidence of infection appears to be changed little. 

This is a comprehensive investigation designed to clarify carcinogenic differences in the mixtures by allowing direct comparisons of Aroclors using current tumor diagnostic criteria, and thereby address some of the limitations in previous studies and problems associated with inter-study comparisons. 

NIST has also used results obtained from inter-laboratory studies as an additional set of results in the two or more methods approach (mode 2 in Table 3.13). For example for the recent value assignment for PCBs and pesticides in SRM 1944, the mean of results from 19 laboratories participating in an inter-laboratory comparison exercise was used as an additional set of data in the determination of the certified values. Similar inter-laboratory study results were also included in the value assignment of PAHs, PCBs, and pesticides for two recently issued mussel tissue materials, SRM 2977 and SRM 2978. 

Ng, C. H. et al. (2005). An inter-ethnic comparison study of clozapine dosage, clinical response and plasma levels. Int. Clin. Psychopharmacol., 20, 163-8. 

The major difficulty in any functional brain studies is inter-subject comparisons. Essentially, all NIR functional brain studies report high variability between subjects. No true comparison can be made due to relative nature of hemodynamic data. Since path length is unknown under MBLL, it is not possible to assess absolute levels of hemodynamic parameters. Instead, each subject is compared with their own baseline measurements. However, generally speaking, the shape of the time evolution of the signals are similar between subjects and thus can be analyzed using qualitative comparisons. 

It should be stressed that inter-laboratory comparisons are not a substitute for regular, in house quality control procedures. Their main value is in novel procedure evaluations or, especially in the present context, when several different laboratories are collaborating in an integrated environmental study. 

In an inter-laboratoiy comparison of PMF based on MALDI-MS and PSA based on LC-MS-MS, a total of 162 2D-GE-separated protein spots from Methanococcus jannaschii and Pyrococcus furiosus were studied [35]. PSA matched 100% of the gel spots, and PMF 97%. Multiple proteins were detected in 9% and 50% of the gel spots by PMF and PSA, respectively. PSA provided better sequence coverage than PMF. 

J. Koziet, A. RoBmann, G.J. Martin, P. Johnson (1995) Determination of the oxygen-18 and deuterium content of fruit and vegetable juice water. An european inter-laboratory comparison study. Anal. Chim. Acta 302. 29-37... 

The Central Chemical Laboratory (CLCh) is the primary analytical facility of the Polish Geological Institute (PIG) and carries out practically all the chemical analysis at PIG. CLCh took part in the INCO-COPERNICUS Project Development of Analytical Procedures to Guarantee Quality Assurance in International Environmental Monitoring . CLCh participated in numerous international inter-laboratory comparisons as well as organized various inter-laboratory comparatives and proficiency testing studies for laboratories of Provincial Environment Protection Inspectorates. In March 2000, CLCh was granted the Certificate of Testing Laboratory Accreditation, with respect to physical and chemical analyses of water. 

Only the apphcation of LC-MS analysis can be conceived of as reliable surfactant analysis. To elaborate determination methods for the analysis of the anionic surfactant mixture of alkyl ethoxysuUates (AES) APCI and ESI-MS(-t/-) studies combined with in-source MS/MS examinations were performed and results were compared (cf. Pig. 15.4 and 15.5 and 15.3.3.2 ESI, surfactants). APCI fragment ion spectra revealed the aUcyl chain length and the number of ethoxylate moieties therefore APCI was found to be the method of choice [326]. To confirm determination methods apphed in surfactant analyses an inter-laboratory comparison study of LC-MS techniques and enzyme-hnked immunosorbent assay for the determination of surfactants in wastewaters was performed in seven laboratories. The quantitative determination of the non-ionic NPEOs, AEOs, coconut diethanol amides (CDEAs) and the anionic LAS, NPEO-sulfates and the secondary alkane sulfonates (SAS) was performed under APCI or ESI-interfacing conditions in positive or negative... 

However, for the agreed cases of inter-laboratory and inter-method comparisons, this review (Muirhead 2000) did propose a study design, together with statistical evalna-tion criteria to assess equivalence, that accounted for interbatch variability and variability within both laboratories or assay procedures. This approach proposed the use of incurred samples, but unfortunately no follow-up publication describing the application of this study design appears to have been published. 

Further studies are needed to confirm the suitability of the in-house matrices as certified reference materials (CRMs). Indeed, there are currently no commercially available CRMs that present a similar texture and chemical composition to the materials Irom the iron and steel industry. An inter-laboratory comparison exercise with external accredited radiochemical laboratories has been organised to support the certification of these materials. 

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