Lieve Van Hoovels1,2, Xavier Bossuyt2,3, Mariangela Manfredi4, Valentina Grossi4, Maurizio Benucci5, Stefanie Van Den Bremt1, Heidi De Baere6, Daria Franceschi6, Emiliano Tosi6, Marco Meoni7, Nicola Bizzaro8, Maria Infantino4. 1. Department of Laboratory Medicine, OLV Hospital, Aalst, Belgium. 2. Department of Microbiology and Immunology, KU Leuven, Leuven, Belgium. 3. Department of Laboratory Medicine, University Hospital Leuven, Leuven, Belgium. 4. Immunology and Allergy Laboratory Unit, San Giovanni di Dio Hospital, Florence, Italy. 5. Rheumatology Unit, S. Giovanni di Dio Hospital, Florence, Italy. 6. A. Menarini Diagnostics, Florence, Italy. 7. Visia Lab Srl, Arezzo, Italy. 8. Laboratorio di Patologia Clinica, Ospedale San Antonio, Tolmezzo, Italy.
Abstract
OBJECTIVES: Currently available computer-aided diagnosis (CAD) systems for the detection of anti-nuclear antibodies (ANA) by indirect immunofluorescence (IIF) assay enable a standardized measurement of system-specific fluorescent intensity (FI) measures. We aimed to evaluate an internal quality control (iQC) program that controls the total ANA IIF process in routine practice. METHODS: In addition to the kit iQC materials, supplemental quality indicators were integrated in a total quality assurance (QA) program: patient-derived iQC's samples (negative, 1/160 fine speckled and 1/160 homogeneous), median sample FI per run and percentage of ANA IIF positive samples per run. Analytical rejection criteria were based on the imprecision of the positivity index (PI) measure of the Zenit PRO system (Menarini). Clinical rejection criteria were based on changes in FI that correspond to a change in ANA IIF titer of ≥2. To evaluate the QA program, different artificial errors were introduced during the ANA IIF process. After every run, quality indicators were evaluated and compared to the pre-set target values. RESULTS: Rescanning the ANA IIF slides five times, using an old conjugate and a needle obstruction resulted in analytically and even clinically relevant errors in ANA IIF results. All errors were correctly detected by the different defined quality indicators. Traditional Westgard rules, including analytically (and clinically) defined rejection limits were useful in monitoring quality indicators. CONCLUSIONS: The integration of a total process iQC program in CAD systems, based on the specific FI measurands and performance criteria of the system, adds value to QA.
OBJECTIVES: Currently available computer-aided diagnosis (CAD) systems for the detection of anti-nuclear antibodies (ANA) by indirect immunofluorescence (IIF) assay enable a standardized measurement of system-specific fluorescent intensity (FI) measures. We aimed to evaluate an internal quality control (iQC) program that controls the total ANA IIF process in routine practice. METHODS: In addition to the kit iQC materials, supplemental quality indicators were integrated in a total quality assurance (QA) program: patient-derived iQC's samples (negative, 1/160 fine speckled and 1/160 homogeneous), median sample FI per run and percentage of ANA IIF positive samples per run. Analytical rejection criteria were based on the imprecision of the positivity index (PI) measure of the Zenit PRO system (Menarini). Clinical rejection criteria were based on changes in FI that correspond to a change in ANA IIF titer of ≥2. To evaluate the QA program, different artificial errors were introduced during the ANA IIF process. After every run, quality indicators were evaluated and compared to the pre-set target values. RESULTS: Rescanning the ANA IIF slides five times, using an old conjugate and a needle obstruction resulted in analytically and even clinically relevant errors in ANA IIF results. All errors were correctly detected by the different defined quality indicators. Traditional Westgard rules, including analytically (and clinically) defined rejection limits were useful in monitoring quality indicators. CONCLUSIONS: The integration of a total process iQC program in CAD systems, based on the specific FI measurands and performance criteria of the system, adds value to QA.