Immunological study of febrile fever: serum sialic acid, immunoglobulin levels [IgA, IgG and IgM], complement factors [C3 and C4] in patients with typhoid fever and brucellosis

ABSTRACT

Typhoid fever and brucellosis are frequent causes of bloodstream infections in many countries. The diagnosis of these infections is challenging because they can have diverse clinical manifestations with symptoms that overlap with a wide spectrum of other diseases. However, neither Widal nor Rose-Bengal agglutination assays are sufficiently sensitive, specific, or practical in areas of endemicity .In this study, it was undertaken to determine the sensitivity and specificity of clinical application of sialic acid in the evaluation of humoral immune response in patients with typhoid fever and brucellosis. Furthermore, the role of sialic acid [SA] was investigated as a possible biological marker and to assist diagnosis of disease. Serum samples from 35 patients with typhoid fever, 35 patients with brucellosis, and 60 healthy s individuals were tested for immunoglobulin A [IgA], IgG and IgM as well as complement factors C3 and C4 by single radial immunodiffusion assay. Determination of serum sialic acid for control, patient and calibration samples was performed by the resorcinol method. The levels of all three classes of immunoglobulin and complement factors were higher in typhoid and brucellosis patients than in healthy individuals, beside significant increases in the serum levels of SA in patients with typhoid fever and brucellosis. There was no significant difference between serum levels of SA in typhoid and brucellosis patients as compared to the control group of healthy individuals. However, we were not able to observe a clinically meaningful difference with respect to sialic acid levels between these two categories. Sialic acid is a general disease marker than a specific marker and the none specificity of increase makes SA determination unsuitable as a specific marker. However it may have a clinical utility, which can be used in conjunction with other test