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Leipzig, Germany

Zegers I.,European Commission | Beetham R.,Frenchay Hospital | Keller T.,ACOMED Statistik | Sheldon J.,Protein Reference Unit | And 5 more authors.
Clinical Chemistry | Year: 2013

BACKGROUND: Different methods for ceruloplasmin tend to give different results in external quality assessment schemes. During the production of the certified reference material ERM-DA470k/IFCC discrepant measurement results were also found for ceruloplasmin measured with different methods, and consequently the protein could not be certified in the material. METHODS: We performed a commutability study with 30 serum samples and the reference materials ERMDA470, ERM-DA470k/IFCC, and ERM-DA472/ IFCC, using 6 different methods. Data were analyzed according to the CLSI Guideline C53-A to assess whether the reference materials had the same behavior as the serum samples with respect to measurement results obtained with combinations of the methods used. RESULTS: Measurement results from different methods showed a good linear correlation for the serum samples. ERM-DA470 showed marked noncommutability for certain combinations of methods. ERMDA470k/ IFCC and ERM-DA472/IFCC were commutable for more combinations of methods. The lack of commutability of ERM-DA470 for certain combinations of methods correlates with results from the UK National External Quality Assessment Service showing discrepancies between results from these methods. For serum stored in the presence of sodium azide the results from different methods are essentially equivalent. CONCLUSIONS: Ceruloplasmin in ERM-DA470 is a fully documented example of a situation in which, due to lack of commutability, the use of a common material for calibration did not lead to harmonization. © 2013 American Association for Clinical Chemistry. Source


Keller T.,ACOMED Statistik | Brinkmann T.,Labor Lademannbogen MVZ GmbH
Clinical Laboratory | Year: 2014

Background: Carryover experiments are widely used for clinical chemistry and immunochemistry analysers to evaluate and validate carryover effects. The experimental design is well described. However, there is no guideline on the statistical approach on data analysis, especially if absence of carryover has to be shown. The only reporting of carryover in ppm is not helpful because its uncertainty is not taken into account. Furthermore, the most commonly used method fails to demonstrate the absence of carryover. We propose a step-by-step guidance applying a new statistical design for analysis of carryover studies based on equivalence testing, and provide a sample based tutorial. Methods: For statistical analysis of carryover effects an one-sided version of equivalence testing by comparing the difference with a predefined limit (i.e., a test of non-superiority) is used. The methodology is demonstrated by measuring total βhCG in human serum samples with a UniCel DxI 880 analyser. Results: A new statistical approach based on equivalence testing has been developed for analysis of data resulting from a typical experimental protocol for carryover studies. Experiments using 8 (11) cycles of high and low concentration samples are appropriate to validate the absence of carryover with 80% (90%) power and an α-level of 0,05 if no carryover is expected. We propose to predefine an acceptance criterion based on the imprecision (here: expressed as one standard deviation) observed for those replicates of the low concentration samples expected to be unaffected by carryover. In the demonstration, the absence of carry-over was concluded with a significance of p < 0.05. Conclusions: Appropriate statistical methods should be applied when the target of a method-validation experiment is (i) absence of any effect, (ii) non-inferiority / non-superiority or (iii) equivalence. Using the example of carryover studies, we show that one-sided equivalence testing is the proper model, and propose a guidance for analysis of these experiments. The example of carryover illustrates a methodology which is also applicable for analysis of a wide range of experimental approaches, including method comparison, commutability and robustness. Source


Denton K.J.,North Bristol NHS Trust | Bergeron C.,Laboratoire Cerba | Klement P.,MTM Laboratories | Trunk M.J.,MTM Laboratories | And 3 more authors.
American Journal of Clinical Pathology | Year: 2010

We analyzed the performance of p16INK4a immunocytochemistry on a series of 810 retrospectively collected atypical squamous cells of undetermined significance (ASC-US) and low-grade squamous intraepithelial lesion (LSIL) cases with available biopsy follow-up data, including 94 cases of cervical intraepithelial neoplasia (CIN) 2 and 128 cases of CIN 3. Human papillomavirus (HPV) testing was performed from the same residual liquid-based cytologic specimen, and results for both tests were correlated with histologic follow-up data. Sensitivity values for high-grade CIN (HGCIN) confirmed on biopsy within 6 months were 92.6% (ASC-US) and 92.2% (LSIL) for cytotechnologists' reviews of p16 cytology and 90.1% (ASC-US) and 95.7% (LSIL) for HPV testing. Sensitivity rates of initial pathologists' reviews were slightly lower, 76.4% to 80.1%, with levels comparable to cytotechnologists' results after adjudication. The specificity of p16 cytology for HGCIN detection was significantly higher than for HPV testing for cytotechnologists and pathologists: 63.2% to 71.1% (p16 cytology) vs 37.8% for HPV in ASC-US (P < .001) and 37.3% to 53.3% (p16 cytology) vs 18.5% for HPV in LSIL (P < .001). This evaluation of the diagnostic performance of p16 cytology confirms the potential of this stain for the efficient triage of ASC-US and LSIL cytologic results. © American Society for Clinical Pathology. Source


Neumann A.,Universitatsklinikum Schleswig Holstein S H | Keller T.,ACOMED Statistik | Jocham D.,Universitatsklinikum Schleswig Holstein S H | Doehn C.,Universitatsklinikum Schleswig Holstein S H
Aktuelle Urologie | Year: 2011

Background:Testicular cancer is the most frequent cancer in patients between 20 and 40years of age. Cure rates are very high due to standardised operative treatment as well as additional chemotherapy and radiotherapy according to histological subtype and tumour stage. Histological subtypes are seminoma, non-seminoma and mixed tumours (partly seminoma and partly non-seminoma). The aim of this study was to determine the value of different tumour markers in the primary diagnosis of testicular cancer. Material and Methods:In a retrospective study we investigated 152consecutive patients with testicular cancer as well as 75patients with benign scrotal conditions. In all patients the tumour markers human alkaline phosphatase (hPLAP), alpha-fetoprotein (AFP), human chorionic gonadotropin (hCG) and the enzyme lactate dehydrogenase (LDH) were measured. Statistical analyses included descriptive analysis, boxplots, fourfold table, receiver operating characteristic (ROC), calculation of confidence intervals and analysis of variance (ANOVA). Results:145patients with a mean age of 34.3years were eligible. There were 72seminomas, 33non-seminomas and 40mixed tumours with 69% of patients being in Lugano stageI, 19% in stageII and 11% in stageIII. hPLAP, AFP and hCG were statistically significantly higher in patients with testicular cancer compared to patients with benign scrotal conditions (p<0.005). hPLAP showed the best sensitivity/specificity (51.1%/84.0%) followed by AFP (35.7%/97.1%), hCG (32.6%/98.6%) and LDH (31.4%/97,8%). ROC analysis demonstrated no difference between hPLAP, AFP and hCG in the specificity range of 80100%. However, a combination of hPLAP, AFP and hCG provided statistically significantly better results than single markers (p<0.001). Conclusion:hPLAP is the most often elevated marker in the serum of patients with testicular cancer and potentially demonstrates a significant benefit for therapy monitoring. In our opinion there is a need to debate the consideration of hPLAP in the usual guidelines of the cancer societies. The unspecific elevation in smokers must be considered. In this regard, reference values of hPLAP depending on smoking habits could be a solution, but valid data are not yet available. © Georg Thieme Verlag KG Stuttgart - New York. Source


Hofmann E.,Universitatsklinikum | Medelnik J.,Universitatsklinikum | Keller T.,ACOMED Statistik | Steinhauser S.,Universitatsklinikum | Hirschfelder U.,Universitatsklinikum
Journal of Orofacial Orthopedics | Year: 2011

Aim: Precise, three-dimensional localization of impacted maxillary canines is central to their clinical management. Predicting precisely the crown's mesiodistal width is paramount in planning orthodontic treatment. The aim of this study was to verify the exact mesiodistal width of impacted canines via MSCT (multislice spiral computed tomography) examinations. Patients and methods: 3D MSCT images from 17 patients with a total of 24 impacted maxillary canines were taken to obtain the largest mesiodistal diameter using mesial and distal contact points. All existing maxillary canines were included in this study. Mesiodistal tooth width was also determined using callipers on a plaster model after canine eruption. Each measurement was taken twice by 3 observers after a 10-day interval. Statistical analysis entailed calculating and comparing the systematic error, intrarater and interrater standard deviations (Deming regression and ANOVA with random effects). Results: Comparison of the different methods revealed good agreement between the pre-eruption and post-eruption values regarding the canine's mesiodistal width. Total standard deviation was 0.16 mm for values obtained from MSCT measurements and 0.12 mm for those taken with callipers. For both methods intrarater measurement error differed by a factor of 2 (repeatability; model versus MSCT: 0.07 mm versus 0.12 mm), while interrater deviation did not differ significantly (reproducibility; model versus MSCT: 0.10 mm versus 0.10 mm). The reproducibility of our measurements whether taken on the model or with CT was below biological variability. Conclusions: The volumetric data from an MSCT system gives highly accurate information on the mesiodistal width of displaced canines. © 2011 Urban & Vogel. Source

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