An Investigation into the Factors Influencing Aerobic Power among Patients with Ankylosing Spondylitis with Special Reference to Respiratory Muscle Performance and Perceived Exertional Dyspnoea

This thesis embraces a series of related studies spanning fourteen months. An initial questionnaire-based survey identified the presence of undue breathlessness perceived in a significant proportion of patients with ankylosing spondylitis (AS). The finding was substantiated by an oxygen-cost diagram study comprising matched healthy controls. Measurements of respiratory muscle strength and endurance were made in a subsequent study. Although maximal strength of the respiratory muscles was preserved in the AS patients, their respiratory muscle endurance during work requiring high inspiratory pressures was clearly impaired. Upright symptom-limited exercise confirmed that exercise tolerance and aerobic power were commonly curtailed among the AS patients. Relative to matched controls, ventilatory response and heart rate response to exercise in the AS patients were raised. However, the elevated ventilatory and heart rate responses were not accompanied by abnormalities in pulmonary gas exchange, breathing reserve, or other cardiocirculatory indices. Although the AS subjects perceived a higher degree of breathing effort for an equivalent level of work rate or ventilation, they were not ventilatory limited. By contrast, the finding of a greater magnitude of leg fatigue perceived among the AS subjects despite achieving a lower work rate strongly suggested a significant element of peripheral musculoskeletal deconditioning. The elevated heart rate response was compatible with an element of cardiac deconditioning secondary to a relative lack of physical activity. Finally, the relative contribution of pulmonary factors, chest restriction, and muscular function to the reduction in aerobic power among the AS patients was quantitively examined. Peripheral muscle strength was found to exert the strongest influence on aerobic power in the AS patients. The addition of lean body mass further improved the variability explained by the regression model derived. No significant influence of impaired respiratory muscle endurance on aerobic power was observed. Vital capacity and limited chest expansion exerted only weak influences on aerobic power in the AS subjects. The results from the studies comprising this thesis thus emphasise the importance of physical activity in this condition. Suggestions for further interventions/strategies of clinical value were made

Adenosine Deaminase Activity Is a Sensitive Marker for the Diagnosis of Tuberculous Pleuritis in Patients with Very Low CD4 Counts

Background: Adenosine Deaminase Activity (ADA) is a commonly used marker for the diagnosis of tuberculous pleural effusion. There has been concern about its usefulness in immunocompromised patients, especially HIV positive patients with very low CD4 counts. The objective of this study was to evaluate the sensitivity of ADA in pleural fluid in patients with low CD4 counts. Materials and Methods: This was a retrospective case control study. Medical files of patients with tuberculous pleuritis and non-tuberculous pleuritis were reviewed. Clinical characteristics, CD4 cell counts in blood and biochemical markers in pleural fluid, including ADA were recorded. Results: One ninety seven tuberculous pleuritis and 40 non- tuberculous pleuritis patients were evaluated. Using the cut-off value of 30 U/L, the overall sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of ADA was 94%, 95%, 19, and 0.06 respectively. The mean CD4 cell counts among TB pleuritis patients was 29 and 153 cells/microL in patients with CD4 ,50 cells/microL and .50 cells/microL, (p,0.05) respectively. The corresponding mean ADA values for these patients were 76 U/L and 72 U/L respectively (p.0.5). There was no correlation between ADA values and CD4 cell counts (r =20.120, p = 0.369). Conclusion: ADA analysis is a sensitive marker of tuberculous pleuritis even in HIV patients with very low CD4 counts in a high TB endemic region. The ADA assay is inexpensive, rapid, and simple to perform and is of great value for the immediate diagnosis of tuberculous pleuritis while waiting for culture result and this has a positive impact on patient outcome

Diagnostic Accuracy of Adenosine Deaminase and Lymphocyte Proportion in Pleural Fluid for Tuberculous Pleurisy in Different Prevalence Scenarios

BACKGROUND: Tuberculous pleural effusion (TPE) is a paucibacillary manifestation of tuberculosis, so isolation of Mycobacterium tuberculosis is difficult, biomarkers being an alternative for diagnosis. Adenosine deaminase (ADA) is the most cost-effective pleural fluid marker and is routinely used in high prevalence settings, whereas its value is questioned in areas with low prevalence. The lymphocyte proportion (LP) is known to increase the specificity of ADA for this diagnosis. We analyse the diagnostic usefulness of ADA alone and the combination of ADA ≥ 40 U/l (ADA(40)) and LP ≥ 50% (LP(50)) in three different prevalence scenarios over 11 years in our area. MATERIALS AND METHODS: Biochemistry, cytology and microbiology studies from 472 consecutive pleural fluid samples were retrospectively analyzed. ADA and differential cell count were determined in all samples. We established three different prevalence periods, based on percentage of pleural effusion cases diagnosed as tuberculosis: 1998-2000 (31.3%), 2001-2004 (11.8%), and 2005-2008 (7.4%). ROC curves, dispersion diagrams and pre/post-test probability graphs were produced. TPE accounted for 73 episodes (mean prevalence: 15.5%). The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for ADA(40) were 89%, 92.7%, 69.2% and 97.9%, respectively. For ADA(40)+LP(50) the specificity and PPV increased (98.3% and 90%) with hardly any decrease in the sensitivity or NPV (86.3% and 97.5%). No relevant differences were observed between the three study periods. CONCLUSIONS/SIGNIFICANCE: ADA remains useful for the diagnosis of TPE even in low-to-intermediate prevalence scenarios when combined with the lymphocyte proportion

18F-NaF and 18F-FDG PET/CT in Gorham-Stout Disease

Gorham-Stout disease (GSD) is an extremely rare skeletal disorder of unknown etiology characterized by benign proliferation of vascular or lymphatic channels, leading to progressive bone resorption. We report on a patient diagnosed with GSD affecting the right scapula and the right ribs, who underwent PET/CT scans using (18)F-FDG and (18)F-NaF. The remnant upper portion of the affected scapula did not show (18)F-FDG uptake, but demonstrated markedly increased (18)F-NaF activity. Furthermore, intense (18)F-NaF activity was seen on the right posterior ribs which were actively being resorbed, suggesting the potential application of (18)F-NaF-PET/CT imaging in GSD diagnosis and follow-up