AddStat: Diagnostic Medicine (Diagnostic studies, Diagnostic accuracy)

... add statistics to your data:   Investigate your diagnostic tests with AddStat's experience!

AddStat is specialized in statistics regarding performance of diagnostic tests. Calculation of sensitivity and specificity using a 2x2 cross table seems to be so easy, however, diagnostic studies are more complex.

Statistical aspects of diagnostic studies

• Defining diagnostic pathway, including reality (Intended use, clinical application, clinical situation)
• Definition of diagnostic accuracs criterion / reference method (gold standard)
• Design of the study - which phase should be chosen?
• Special designs of diagnostic studies - e.g. multi-reader-multi-case (MRMC), verification of only positively tested (VOPT)
• Inclusion and exclusion criteria: "case control" (known disease) vs. "cohort" (suspected to have disease)
• Sample size estimation (internal tools, software Medcalc®, PASS)
• Criteria for cut-off determination
• Biases due to selection, non-perfect reference method, missing diagnostic accuracy criterion, sub-groub-analyses, inclusion criteria
• Design of data entry, data management, data validation, data transfer
• Documentation, Design of CRF
• Analysis of ROC curve, cut-off-determination

Statistical analyses (ROC curve, partial AUC, DAC method, cut-off etc.)

• Calculation of ROC curve, estimation of AUC
• Calculation of partial ROC curve, estimation of partial AUC
• Comparison of ROC-curves
• Comparison of diagnostic tests by DAC method (Discordancy analysis characteristics)
• Comparison of sensitivity / specificity (McNemar-Tests)
• Cut-off estimation

All these analyses are conducted according to an internal GCP compliant SOP-system.

Statistical analyses are performed using following software: SAS¬ (if requested, also in Medcalc®, SPSS® 15.0/18.0, NCSS and R.)

Using SAS®, AddStat can provide analyses performed under regulated conditions (complete traceability, formal exclusion of any manipulation of data and output).

Further information about ROC analysis and related tools you can obtain from following web-sites about ROC curves (in German) and Excel-tools for ROC analysis