RESUMO
Background: Power Doppler ultrasound (PDUS) is an established non-invasive modalities for quantification of inflammation, which has a bearing on the assessment of disease activity in rheumatoid arthritis (RA). However, PDUS has several disadvantages including cost of equipment, steep learning curve and inter-observer variability. Thermal imaging has emerged as a simple, powerful tool for mapping the heat distribution pattern and has the potential to document and quantify disease activity in RA. The objective was to study the thermal imaging pattern of inflamed knee joints in cases of RA and its correlation with PDUS. Methods: This pilot case-control study was carried out at the rheumatology centre in India including 100 subjects (50 controls and 50 RA patients). All participants underwent thermal imaging and PDUS for the knee joints. The mean temperatures in area of interest in knee, thigh and knee-thigh differential were analysed in comparison with PDUS findings. Results: RA subjects had significantly higher mean knee temperature and mean knee-thigh temperature differential compared with controls (p value < 0.00001). PDUS documented inflammation strongly correlated with knee-thigh temperature differential. Conclusion: There was a statistically significant difference in mean knee temperature as well as mean knee-thigh temperature differential of inflamed versus control knees. Thermal imaging has the potential to become simple, objective, cost-effective and reliable tool for diagnosis and assessment of disease activity in inflammatory arthritis.
RESUMO
Background: There is lack of Indian data on diagnostic utility of rheumatoid factor (RF) and anti-citrullinated protein antibody (ACPA) for diagnosis of rheumatoid arthritis (RA) and prevalence of these antibodies in patients with RA and the healthy population. The study was aimed to assess the diagnostic utility and prevalence of RF and ACPA at different titers in the Indian scenario. Method: All the patients of RA fulfilling the European League Against Rheumatism/American College of Rheumatology (EULAR/ACR) 2010 classification criteria and age and gender-matched healthy controls were included in the study. RF and ACPA were measured by nephelometry and the enzyme-linked immunosorbent assay (ELISA) method, respectively. Result: Of 803 patients (291 men and 512 women) included, the RF was positive in 566 (70.5%) study patients. The ACPA was positive in 527 (71.7%) patients of 735 of them. Among 408 healthy controls, 45 (11%) were RF positive and 19 (4.7%) were ACPA positive.At the positive cutoff level, the RF had a specificity of 87.6% (95% confidence interval [CI] = 84.4-90.8; positive likelihood ratio [LR+] 5.7). Specificity at 2 and 3 times above the upper limit of normal (ULN) increased to 96.2% (95% CI = 94.3-98.1; LR+ 15.7) and 97.1% (95% CI = 95.5-98.7; LR+ 17.1), respectively.The specificity of ACPA at the positive cutoff level was 94.4% (95% CI = 92.2-96.6; LR+ 12.7), which increased to 98% (95% CI = 96.6-99.4), at 2xULN level. The likelihood ratio for ACPA at all cutoff levels measured was more than 10. Conclusion: The sensitivity and specificity of RF and ACPA in our study population are comparable with those of other studies. ACPA at lower titers may have sufficient diagnostic utility for RA in an appropriate clinical setting.
