Simple dipstick assay for the detection of Salmonella typhi-specific IgM antibodies and the evolution of the immune response in patients with typhoid fever.

Abstract

Abstract. Application of a dipstick assay for the detection of Salmonella typhi-specific IgM antibodies on samples collected from S. typhi or S. paratyphi culture-positive patients at the day of admission to the hospital revealed the presence of specific IgM antibodies in 43.5%, 92.9%, and 100% for samples collected 4-6 days, 6-9 days, and > 9 days after the onset of fever, respectively. The mean sensitivity for samples collected an average of 6.6 days after the onset of fever was 65.3%. Culture was positive in 65.9% of the cases with a final clinical diagnosis of typhoid fever. Testing of paired serum samples from culture negative patients with a final clinical diagnosis of typhoid fever resulted in staining of the dipstick in 4.3% of the samples collected at the day of admission to the hospital and in 76.6% of the samples collected one week later, thereby provided strong supporting evidence of typhoid fever by demonstrating seroconversion in a large proportion of the patients. The dipstick assay may thus also be useful for the serodiagnosis of culture-negative patients with clinical signs and symptoms consistent with typhoid fever. The advantages of the dipstick assay are that the result can be obtained on the same day allowing a prompt treatment, that only a small volume of serum is needed, and that no special laboratory equipment is needed to perform the assay. The stability of the reagents of the dipstick and the simplicity of the assay allows its use in places that lack laboratory facilities.

Comparative study of Dot enzyme immune assay and Widal test in the diagnosis of Typhoid fever in a tertiary care hospital in south Kerala

“…An evaluation of ICT in India was found to be 100% sensitive and 80% specific compared to a blood culture as gold standard 12 Another study conducted in Department, Naval Medical Research Center, Silver Spring, Maryland shows two positive scrub typhus in acute febrile illness patients out of 167 positive typhoid cases 16 .…”

“…The cross reactive samples were ICT negative. ICT has been evaluated in many countries and they found significantly higher sensitivity and specificity 11,12,13 .…”

Laboratory Diagnosis of Enteric Fever: A Review Update

“…Commercially it is available in two different properties like the Typhidot M that detects only IgM antibodies of S. typhi has been reported to be slightly more specific in a couple of studies [48][49] . Typhidot® test detects specific IgM and IgG antibodies to S. typhi.…”

“…A rapid dipstick assay for the detection of S. typhispecific IgM antibodies in serum and whole blood samples was previously reported and the sensitivity and specificity was evaluated 47,49 . The dipstick assay may thus also be useful for the serodiagnosis of culture-negative patients with clinical signs and symptoms consistent with typhoid fever.…”

“…The advantages of the dipstick assay are that the result can be obtained on the same day allowing a prompt treatment, that only a small volume of serum is needed, and that no special laboratory equipment is needed to perform the assay. The stability of the reagents of the dipstick and the simplicity of the assay allows its use in places that lack laboratory facilities 49 .…”