ABSTRACT
While mortality and morbidity from pulmonary tuberculosis (PTB) have improved, diagnosis of this infectious disease remains suboptimal without a point-of-care test. Antibody/ antigen-based serodiagnostics is the most amenable for point-of-care translation but hampered by a lack of validated biomarkers and a heterogeneous patient antibody response. Using a case-control design, we assessed serodiagnostic potential of immunoglobulins G, A, and dimeric IgA responses against 18 antigenic preparations, followed by antibody-subclass responses against antigen 60 (A60), and four markers of host innate immunity by enzymelinked immunoassay using sera samples (n=110) collected from April to October 2007 in VietNam from human immunodeficiency-negative patients with provisional diagnosis of PTB. We further analyzed host variables to investigate factors driving biomarker heterogeneity observed in patients. Among active pulmonary tuberculosis patients, low correlation was observed between anti-A60 antibody-classes, and between anti-A60 immunoglobulin G subclasses, but anti-A60 immunoglobulin A subclasses were significantly correlated. The best diagnostic combination of anti-A60 immunoglobulin G/A and a C-reactive protein “ruleout” remains insufficient at 82%/92% sensitivity/specificity (95%CI: 72-92%/82-98%). Heterogeneity of anti-A60 immunoglobulins G2, G3, M, as well as C-reactive protein and serum amyloid A levels observed in this study population appeared to be significantly associated with history of previous tuberculosis, hemoptysis, age, vaccination, night sweats, smoking, chest pain, fever, alcohol, and solid culture count. Further research on tuberculosis serological biomarkers may require consideration of host factors and new approaches using multiple biomarkers.
ABSTRACT
Sputum induction with nebulized hypertonic saline is increasingly being used to evaluate airway inflammation. We investigated the procedure-associated risk in 16 asthmatics that were still symptomatic despite on high doses of regular corticosteroid (CS) therapy (7 on daily inhaled CS > or = 800 microg budesonide or equivalent; 9 on additional daily oral CS) and their sputum cellular profile. For comparison, 12 mild stable asthmatics and 10 normal healthy subjects were included. All subjects inhaled 3%, 4% and 5% hypertonic saline sequentially via ultrasonic nebulizer as a means to induce sputum. Maximal percentage fall of Forced Expiratory Volume on One Second (FEV1) during sputum induction was significantly greater in CS-dependent asthmatics (median % [IQR]: 16.0 [11.0-32.3]) than in mild asthmatics (5.3 [4.2-10.8], p = 0.002] and in normal subjects (4.6 [3.4-6.4]), p = 0.0001). The maximal percentage FEV1 fall was inversely correlated with baseline FEV1 (Rs= -0.69; p < 0.0001). Compared to mild asthmatics, induced sputum from CS-dependant asthmatics had proportionately fewer eosinophils (2.2 [0.8-7.0] versus 23.3% [10.7-46.3], p = 0.003) and greater neutrophils (64.2 [43.9-81.2] versus 28.7 [19.0-42.6], p = 0.009). Sputum neutrophils showed a significant inverse correlation to FEV1 (Rs = -0.51, p = 0.01). We concluded that sputum induction using nebulized hypertonic saline should be performed with caution in CS-dependant asthmatics. The airway cellular profile observed suggests that the immunopathology underlying CS-dependant asthmatics may be different or a consequence of CS therapy.