Utility of biomarkers and temporal artery biopsy length for investigating giant cell arteritis in Western Australia.

AIM: To explore demographic characteristics, biopsy length, and blood biomarker performance in an Australian cohort of patients who have undergone temporal artery biopsy (TAB) for giant cell arteritis (GCA). METHODS: We extracted data on biopsies performed for GCA between January 2016 and December 2020 at public hospitals in Perth. Sensitivity, specificity, and area under the curve (AUC) were calculated for blood results. We evaluated the proportion of biopsies with post-fixation length less than 15 mm and explored several length associations. RESULTS: We retrospectively reviewed biopsies of 360 patients (65.8% female, mean age 72.1 years). Biopsy-positive patients were older (6.0 years, P < 0.01), and had higher C-reactive protein (CRP) (44.5 mg/L, P < 0.01), erythrocyte sedimentation rate (ESR) (18.9 mm/h, P < 0.01), and platelets (86.8 × 103 /µL, P < 0.01) compared with biopsy-negative patients. CRP and platelets had the highest AUCs at 0.76 and 0.71, respectively. Sensitivities for CRP and ESR were 96.2% and 91.5%, respectively. Specificities were comparatively low at 41.3% for CRP and 37.4% for ESR. The proportion of biopsies with sub-optimal length was 55.9% and this varied significantly by site (P < 0.01). Smaller sites performed worse, with a sub-optimal biopsy rate of 87% amongst the three smallest sites. CONCLUSION: ESR and CRP are helpful preliminary investigations, especially in identifying low-risk patients, but their specificity is limited. Smaller centers had a higher proportion of biopsies with sub-optimal length. Considering the importance of biopsy length for TAB diagnostic value, reviewing biopsy data may assist services in developing improvement strategies.

Expression of cardiac alpha-actin spares extraocular muscles in skeletal muscle alpha-actin diseases--quantification of striated alpha-actins by MRM-mass spectrometry.

As with many skeletal muscle diseases, the extraocular muscles (EOMs) are spared in skeletal muscle alpha-actin diseases, with no ophthalmoplegia even in severely affected patients. We hypothesised that the extraocular muscles sparing in these patients was due to significant expression of cardiac alpha-actin, the alpha-actin isoform expressed in heart and foetal skeletal muscle. We have shown by immunochemistry, Western blotting and a novel MRM-mass spectrometry technique, comparable levels of cardiac alpha-actin in the extraocular muscles of human, pig and sheep to those in the heart. The sparing of extraocular muscles in skeletal muscle alpha-actin disease is thus probably due to greater levels of cardiac alpha-actin, than the negligible amounts in skeletal muscles, diluting out the effects of the mutant skeletal muscle alpha-actin.

Tamoxifen optic neuropathy.

A 68-year-old woman with metastatic breast cancer presented with slowly progressive visual loss in each eye. Electrophysiology confirmed bilateral optic neuropathies. Investigations to determine the cause of the vision loss were negative. Cessation of tamoxifen resulted in a dramatic improvement in acuity.