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Published on: February 4, 2012
Performance characteristics of the PolyTiter Immunofluorescent Titration system for determination of antinuclear
Karen A Flessland1, Helen R Landicho, Kimberlee K Borden
1Alidex, Inc., Redmond, Washington 98052, USA. kflessland@alidexinc.com
Insights
The PolyTiter system offers a reliable method for quantifying antinuclear antibodies (ANA) in immunofluorescent assays (IFA). This system provides accurate endpoint titers directly from a 1:40 dilution, simplifying routine clinical laboratory testing.
Area of Science:
- Immunology
- Clinical Diagnostics
- Laboratory Medicine
Background:
- Conventional antinuclear antibody (ANA) screening uses immunofluorescent (IF) microscopy with serial dilutions.
- Quantifying IF staining intensity traditionally involves twofold serial dilutions to determine endpoint titers.
- This process can be time-consuming and subject to variability.
Purpose of the Study:
- To evaluate the performance characteristics of the PolyTiter Immunofluorescent Titration system for ANA-IF assay (IFA) testing.
- To compare the PolyTiter system's accuracy and precision against conventional serial dilution methods.
- To assess the system's suitability for routine use in clinical laboratories.
Main Methods:
- The PolyTiter system relates IF staining intensity to reference calibrators for direct endpoint titer determination from a 1:40 dilution.
- Two technologists performed replicate evaluations of specimens and controls over five days.
- Performance was assessed by endpoint dilution agreement, precision analysis (coefficients of variation), and lot-to-lot variation.
Main Results:
- Endpoint dilution agreement with the reference was 100% for controls and high-specimen samples by one technologist, and 98-100% for others.
- Between-reader, between-run, and within-run precision coefficients of variation were below 10%.
- Overall agreement between PolyTiter and serial dilution for 125 specimens was 86-93%, with similar pattern identification.
Conclusions:
- The PolyTiter system demonstrates acceptable performance for routine ANA-IFA testing.
- It offers a reliable and potentially more efficient alternative to traditional serial dilution methods.
- The system provides accurate and reproducible results for ANA antibody quantification.
Abstract:
Conventional screening for circulating antinuclear antibodies (ANA) is generally performed by immunofluorescent (IF) microscopy with a 1:40 dilution of serum. Intensity of IF staining is then semiquantitated by using twofold serial dilutions, where the highest dilution in which staining intensity equals the endpoint control is expressed as an endpoint titer. The PolyTiter Immunofluorescent Titration system (Polymedco, Inc.) facilitates ANA-IF assay (IFA) testing by relating the intensity of IF staining to reference calibrators (defined in PolyTiter units), providing an endpoint titer directly from a 1:40 dilution. This study was conducted to assess the performance characteristics of the PolyTiter system. Two technologists each evaluated 10 replicates of three specimens and two controls on five sequential days. Endpoint dilution agreement (defined as +/-2 dilutions) with the reference was 100% for all controls and for all specimens by one technologist. The second reader reported agreement of 98, 88, and 100% for the low, medium, and high specimens, respectively. Analysis of PolyTiter unit values yielded between-reader, between-run, and within-run precision coefficients of variation of less than 10%. The variance component in the lot-to-lot analysis was zero, indicating all of the variation was due to run-to-run differences. Overall endpoint dilution agreement between PolyTiter and serial dilution in the evaluation of 125 specimens at three sites was 90, 93, and 86%. Pattern identification with the PolyTiter was similar to that with serial dilution. The PolyTiter system demonstrates acceptable performance for routine ANA-IFA testing in the clinical laboratory.
