Flow Cytometric Human Leukocyte Antigen-B27 Typing with Stored Samples for Batch Testing

BACKGROUND: Flow cytometry (FC) HLA-B27 typing is still used extensively for the diagnosis of spondyloarthropathies. If patient blood samples are stored for a prolonged duration, this testing can be performed in a batch manner, and in-house cellular controls could easily be procured. In this study, we investigated various methods of storing patient blood samples. METHODS: We compared four storage methods: three methods of analyzing lymphocytes (whole blood stored at room temperature, frozen mononuclear cells, and frozen white blood cells [WBCs] after lysing red blood cells [RBCs]), and one method using frozen platelets (FPLT). We used three ratios associated with mean fluorescence intensities (MFI) for HLAB27 assignment: the B27 MFI ratio (sample/control) for HLA-B27 fluorescein-5-isothiocyanate (FITC); the B7 MFI ratio for HLA-B7 phycoerythrin (PE); and the ratio of these two ratios, B7/B27 ratio. RESULTS: Comparing the B27 MFI ratios of each storage method for the HLA-B27+ samples and the B7/B27 ratios for the HLA-B7+ samples revealed that FPLT was the best of the four methods. FPLT had a sensitivity of 100% and a specificity of 99.3% for HLA-B27 assignment in DNA-typed samples (N=164) when the two criteria, namely, B27 MFI ratio >4.0 and B7/B27 ratio <1.5, were used. CONCLUSIONS: The FPLT method was found to offer a simple, economical, and accurate method of FC HLA-B27 typing by using stored patient samples. If stored samples are used, this method has the potential to replace the standard FC typing method when used in combination with a complementary DNA-based method.

Flow Cytometric Human Leukocyte Antigen-B27 Typing with Stored Samples for Batch Testing

BACKGROUND: Flow cytometry (FC) HLA-B27 typing is still used extensively for the diagnosis of spondyloarthropathies. If patient blood samples are stored for a prolonged duration, this testing can be performed in a batch manner, and in-house cellular controls could easily be procured. In this study, we investigated various methods of storing patient blood samples. METHODS: We compared four storage methods: three methods of analyzing lymphocytes (whole blood stored at room temperature, frozen mononuclear cells, and frozen white blood cells [WBCs] after lysing red blood cells [RBCs]), and one method using frozen platelets (FPLT). We used three ratios associated with mean fluorescence intensities (MFI) for HLAB27 assignment: the B27 MFI ratio (sample/control) for HLA-B27 fluorescein-5-isothiocyanate (FITC); the B7 MFI ratio for HLA-B7 phycoerythrin (PE); and the ratio of these two ratios, B7/B27 ratio. RESULTS: Comparing the B27 MFI ratios of each storage method for the HLA-B27+ samples and the B7/B27 ratios for the HLA-B7+ samples revealed that FPLT was the best of the four methods. FPLT had a sensitivity of 100% and a specificity of 99.3% for HLA-B27 assignment in DNA-typed samples (N=164) when the two criteria, namely, B27 MFI ratio >4.0 and B7/B27 ratio <1.5, were used. CONCLUSIONS: The FPLT method was found to offer a simple, economical, and accurate method of FC HLA-B27 typing by using stored patient samples. If stored samples are used, this method has the potential to replace the standard FC typing method when used in combination with a complementary DNA-based method.

The Experience of HLA-B27 Test Using Flowcytometry / 임상검사와정도관리

BACKGROUND: HLA-B27 is associated with an increased incidence of specific spondyloarthropathies(SpA), most notably ankylosing spondylitis(AS). I evaluated the cases referred for HLA-B27 antigen using flowcytometry (FCM) to find the clinical characteristics of the patients and the diagnostic utilities of median fluorescence intensity (MFI) in HLA-B27 program. METHODS: I evaluated 443 subjects of HLA-B27 cases using FACScan flowcytometry, consisted with software for automated calibration and analysis, calibration beads, and the anti-HLA- B27 fluorescein isothiocyanate (FITC)/anti-CD3 phycoerythrin (PE) monoclonal antibodies (all from Becton Dickinson, San Jose, CA). RESULTS: Of the total 443 cases, the positive rate in male cases was 44% (132/300) and it was higher than that of female cases (22.4%, 32/143). The gating procedure was failed in one sample of 443 (0.23%). The positive rates in each diagnostic criteria were as follows; AS 61.6%, gout 20.0%, herniated intervertebral disc 20%, lower back pain 25.6%, polyarthritis 16.0%, psoriatic arthritis 20.0%, rheumatoid arthritis 28.3%, reactive arthritis 26.9%, SpA, undifferentiated 31.8% and uveitis/iritis 23.8%. In AS group, 89 cases (95.7%) showed MFI values higher than 150. CONCLUSION: About 62% of AS group showed HLA-B27 positivity using FCM and the positive rates of other diseases group in SpA categories were around 20-30%. If we considered MFI value 150 as differential value, about 95% of HLA-B27 positive AS cases might not need further confirmatory study to differentiate HLA-B7.

Comparison of HLA-B27 typing methods -PCR-SSP, microlymphocytotoxicity, and flow cytometry / 대한임상병리학회지

BACKGROUND: HLA-B27 typing has long been performed by the microlymphocytotoxicity method(MCT) but the flow cytometry method(FCM) was introduced several years ago. False positive results due to the HLA-B7 cross reactive groups(CREG) were the main drawback of the serologic method. The authors performed polymerase chain reaction-sequence specific primer(PCR-SSP) test for HLA-B27 to compare the results with serologic methods. METHODS: PCR-SSP test for HLA-B27 was performed on four hundred forty one samples. Three hundred twenty eight samples were tested by MCT and one hundred thirteen samples by FCM. PCR-SSP for HLA-B27 subtyping or Amplification Refractory Mutation System-PCR(ARMS-PCR) for HLA-B typing was performed on twenty four discrepant samples. RESULTS: The concordance rate between MCT and PCR-SSP was 92.9%(305/328) and the concordance rate between FCM and PCR-SSP was 99.1%(112/113). Twenty four(5.4%) out of four hundred forty one samples showed discrepancy between serologic methods and PCR-SSP method. Fourteen out of one hundred MCT positive samples and only one out of forty FCM positive samples showed negative by PCR-SSP. Nine samples showed PCR-SSP positive and MCT negative. CONCLUSIONS: The false positive rate of MCT was quite high and there were some false positive and negative results by PCR-SSP, too. From the above findings, we suggest that FCM is the most accurate method for HLA-B27 typing in those laboratory equipped with flow cytometry.

Quantitation of HLA antigens on red cells by immunoradiometric assay.

Immunoradiometric assay was employed to quantitate HLA antigens on red cells. Using this technique HLA-B7, HLA-B17 and HLA-A28 were detected on the red cells of all individuals studied irrespective of the serological status of the Bennett-Goodspeed (Bg) antigens. However, HLA antigenic sites for serologically Bg positive red cells were significantly more than that for Bg negative red cells (P less than 0.001). Bga positive red cells possessed maximum number of antigenic sites as compared to Bgb and Bgc positive red cells.