Diagnostic Accuracy of a Loop-Mediated Isothermal PCR Assay for Detection of Orientia tsutsugamushi during Acute Scrub Typhus Infection

There is an urgent need for alternative diagnostic methods for scrub typhus, but evaluation of these is hampered because the current serological gold standard (IFA) is imperfect. In a study from Thailand, 3 of 20 (15%) patients with fever had a positive Orientia tsutsugamushi PCR result despite negative serology. These findings could reflect potential benefits of the PCR assay in detecting rickettsaemia before antibody responses set in and/or a diagnostic advantage in endemic areas with high background levels of antibody in the population. Serology is complicated by the heterogeneity of strains present in Southeast Asia, but high resource costs and training make realtime PCR assays impractical for many areas where scrub typhus is endemic. This is where the new LAMP methodology has potential: it is inexpensive, simple to perform and requires only a waterbath or simple heating block instead of a thermocycler. In the context of a prospective fever study in a scrub typhus-endemic area in Thailand, the results support the validity of LAMP methodology for the diagnosis of scrub typhus, highlight the difficulties in comparing antibody- with DNA-based methods and also contribute towards understanding the dynamics of bacteraemia in this under recognised and under studied disease

Life expectancy after initiation of combination antiretroviral therapy in Thailand

Background: Access to combination antiretroviral therapy (cART) has decreased mortality in HIV-positive people. We aimed to estimate the expected additional years of life in HIV-positive Thai people after starting cART through the National AIDS Program (NAP), administered by the Thai National Health Security Office (NHSO). Methods: The NHSO database collects characteristics of all Thai HIV-infected patients through the National AIDS Program, including linkage with the National Death Registry for vital status. This study included patients aged >= 15 years at cART initiation between 2008 and 2014. The abridged life table method was used to construct life tables stratified by sex and baseline CD4(+) T-cell count. Life expectancy was defined as the additional years of life from age at starting cART. Results: 201,688 eligible patients were included in analyses, contributing 618,837 person-years of followup. Median CD4(+) T-cell count was 109 cells/mm(3) and median age 37 years. The overall life expectancy after cART initiation at age 20 was 25.4 (95% CI, 25.3, 25.6) years and 20.6 (95% CI, 20.5, 20.7) at age 35 years. Life expectancy at baseline CD4(+) T-cell count >= 350 cells/mm(3) was 51.9 (95% CI, 51.0, 52.9) years for age 20 years and 43.2 (95% CI, 42.4, 44.1) years for age 35 years, close to life expectancy in the general Thai population. Conclusions: Increasing life expectancy with higher baseline CD4(+) T-cell counts supports the guideline recommendations to start cART irrespective of CD4(+) T-cell count. These results are beneficial to forecast the treatment cost and develop health policies for people living with HIV in Thailand and Asi

Overall and positivity percent agreement of LAMP results, when compared with other modalities.

<p>The cohort consists of 161 clinical prospectively collected samples, follow-up sera were available for 138/161 (86%) samples. Probability values for the comparison of positivity rates for LAMP with the other assays were determined using McNemar's test: p-values in <b>bold</b> indicate that the proportion of LAMP positives and the proportion of the tested modality positives are significantly different, i.e. a low level of agreement.</p

Dissection of discrepant LAMP assay results according to the ‘scrub typhus infection criteria’ (STIC).

<p>The LAMP results of each individual sub-group of STIC were grouped into positive/negative to allow for comparisons to other diagnostic modalities. Serological median reciprocal admission (Adm) and follow-up (Fup) IgM titers are shown as well as supportive diagnostic evidence from PCR, isolation and rapidtests (percentage of positive results). Discrepancies had no association with ‘days of fever / illness’ prior to admission.</p

Effect of sample timing on admision diagnostic positivity rates.

<p>Sample timing in terms of ‘days of fever prior diagnosis’ was significantly associated with LAMP positivity rates. Overall, the LAMP assay was superior at demonstrating positivity up 8 days of fever prior admission. Combination of the LAMP assay and the PanBio IgM ICT rapid test improved the overall sensitivity and expanded the temporal spectrum of <i>O. tsutsugamushi</i> detection in the acute setting.</p