Atmospheric NO_2 Concentration Measurements Using Differential Absorption Lidar Technique

Using the Differential Absorption Lidar (DIAL) technique, two types of approaches, namely, reflection from retroreflector / topographic target and backscatter from atmosphere, are available for studying remotely the atmospheric NO, concentration. The Argon ion lidar system at the Indian Institute of Tropical Meteorology (IITM), Pune, India has been used for the measurements by following both the path-averaged and range-resolved approaches. For the former, a topographic target (hill) is used for determining path-averaged surface concentration. In the latter, spectral properties of atmospheric attenuation is used for making range-resolved measurements in the surface layer. The results of the observations collected by following both approaches are presented. The average surface NO2 concentration was found to vary between 0.01 and 0.105 ppm and the range-resolved measurements exhibited higher values suggesting treatment of the lidar data for scattering and extinction effects due to atmospheric aerosols and air molecules, and atmospheric turbulence. Certain modifications that are suggested to the experimental set-up, data acquisition and analysis to improve the measurements are briefly described.

Accuracy of a new rapid diagnostic test for urinary antigen detection and assessment of drug treatment in opisthorchiasis

Background Screening for opisthorchiasis,a parasitic worm infection affecting many millions of people in Southeast Asia,has traditionally relied on faecal egg examination such as the formalin-ethyl acetate concentration technique(FECT)and Kato-Katz method.Although the urinary enzyme-linked immunosorbent assay(ELISA)has been used more recently,we developed a urinary antigen-based rapid diagnostic test(RDT)to simplify diagnosis and as a point-of-care testing(POCT)and field applications for surveillance and control of opisthorchiasis.Methods A urinaryOpisthorchis viverrini(OV)-RDT was developed using immunochromatographic methodology with a specific monoclonal antibody against OV.The diagnostic performance of the urinary OV-RDT was compared to that of quantitative faecal FECT and urinary antigen ELISA(n=493).Cross-reactivities of urinary OV-RDT with other helminthiases coexisted withO.viverrini were determined(n=96).A field trial in the application of urinary OV-RDT was compared with urinary antigen ELISA at baseline screening and assessment of drug treatment outcomes in opisthorchiasis(n=1629).The McNemar chi-square,Kruskal-Wallis and Cohen’s kappa coefficient(κ-value)tests were used for statistical analyses.Results Urinary OV-RDT had sensitivity of 94.2%and specificity of 93.2%,compared to faecal FECT.Urinary OV-RDT had high diagnostic agreement(Kappa=0.842-0.874,P<0.001)and quantitative correlation with urinary antigen ELISA(Kruskal-Wallis tests=316.2,P<0.0001)and faecal FECT(Kruskal-Wallis tests=362.3,P<0.0001).The positive rates by OV-RDT,ELISA and FECT were 48.9%,52.5%and 49.3%,respectively.Cross-reactions of urinary OV-RDT with other helminthiases were few(2%).Field trials of urinary OV-RDT yielded comparable prevalence ofO.viverrini between urinary OV-RDT(53.2%)and urinary antigen ELISA(54.0%).OV screening showed high diagnostic agreement(kappa>0.8,P<0.0001)between urinary OV-RDT and urinary antigen ELISA.The cure rates of opisthorchiasis at 1 month post-praziquantel treatment determined by urinary OV-RDT(86.6%)and urinary antigen ELISA(80.5%)were similar(P>0.05).Conclusions The urinary OV-RDT test has high potential as a new tool for screening and evaluating treatment outcomes in opisthorchiasis.The ease of sample collection and simplicity of urinary OV-RDT may facilitate mass screening,control and elimination of opisthorchiasis,thereby contributing to a reduction in the disease burden in Southeast Asia.