Does adding anti-F actin antibody assay to the testing protocol help in diagnosis and monitoring of patients with Autoimmune Hepatitis?
Background
Autoimmune hepatitis (AIH) is a disease that effects around 0.025% of the population. Without treatment the autoimmune response can cause progressive liver damage and deterioration of liver function leading to cirrhosis which can ultimately prove fatal.
Diagnosis can be challenging due to the heterogeneity of presentation. Four diagnostic indicators are used raised immunoglobulins, absence of viral hepatitis, liver histology compatible with AIH and presence of autoantibodies (ANA, SMA or LKM).
Objective
Smooth muscle antibodies are the predominant autoantibody found in AIH, with those directed against F-actin proposed to be the most clinically significant. This study assessed three F-actin specific assays to ascertain whether they could replace or enhance the current immunofluorescence testing method.
Method
Sera of 133 patients who had liver autoantibody test requests were collected and tested using the current methodology and the three new assays. Current practice utilizes rodent liver kidney stomach tissue indirect immunofluorescence (IFA) microscopy to distinguish tubular staining pattern (F-actin specific) from that of a vascular staining pattern. This study assessed three F-actin specific assays (Euroimmun VSM47 IFA, INOVA NOVALite IgG F-actin IFA and the INOVA QUANTALite IgG F-actin ELISA).
All the results generated were designated positive, negative or equivocal to allow comparison between methods. Their performance was assessed against the current method and the clinical outcome (whether the patient had AIH). Qualitative results from the ELISA were analysed to determine optimal cutoff value using Youden’s J.
Results
All three assays showed strong correlation with a diagnosis of AIH (p=<0.05). Cohens Kappa showed good correlation with the current method.
The specificity (Sp) and sensitivity (Se) of each as a stand-alone assay was similar or improved when compared to the current LKS method (Sp=81.31%, Se= 86.67%), VSM 47 (81.31%, 92.86%), NOVALite (85.98%, 85.71%), QUANTALite cutoff <20 (80.37%, 92.86%), QUANTALite cutoff <30 (93.46%, 85.71%), QUANTALite using optimal cutoff <28.18 (90.74,%, 100%) with the QUANTALite using optimal cutoff <28.18AU showing the best performance. In all circumstances the specificity improved when a confirmatory second line test was added. The QUANTALite using optimal cutoff <28.18AU following a positive SMA (all patterns), identified 100% of AIH positive patients and showed to be 92% specific for the disease. The specificity was 98% if the initial pattern observed was Tubular type.
Conclusions
All three assays would be suitable as first line screening for AIH-1, although the realities of liver autoantibody screening mean this would be impractical currently. All three assays would provide clinical benefit as a second line test, especially the ELISA with the altered cutoff of 28AU.
History
Qualification name
- MRes
Supervisor
Dr Rochelle Hockney Dr Ian HurleyAwarding Institution
Leeds Beckett UniversityCompletion Date
2024-12-19Qualification level
- Masters
Language
- eng