Soil Organic Carbon Estimation using VIS–NIR–SWIR Spectroscopy: The Effect of Multiple Sensors and Scanning Conditions

Visible–near infrared–shortwave infrared (VIS–NIR–SWIR) spectroscopy is being increasingly used for soil organic carbon (SOC) assessment. Common practice consists of scanning soil samples using a single spectrometer. Considerations have rarely been documented of the effects of using multiple instruments and scanning conditions on SOC model calibration that occur when merging soil spectral libraries (SSLs), particularly in soils with low SOC concentration and using both field spectroradiometers and laboratory fixed spectrometers. To address this gap, we scanned 143 low-SOC-content soil samples using three spectrometers (ASD FieldSpec 3, ASD FieldSpec 4, and FOSS XDS) and four setup features - FOSS, contact probe (CP), dark-box (DB), and open laboratory (LAB) - at three laboratories. The application of an internal soil standard (ISS) to align one laboratory spectrum with another for spectral correction and spectral merging of various SSLs was examined. SOC models were developed using i) data from each single spectrometer – single laboratory separately and ii) merged data from multiple spectrometers – different laboratories, applying the 1st derivatives of spectra and random forest (RF) regression. The results indicate that the spectral shape and position obtained from all spectrometers and setups did not show any noticeable differences, though spectra based on FOSS setup, particularly on low-SOC samples, demonstrated the highest absolute derivative values regardless of ISS application. The derivative ISS-corrected spectra showed less variation among different spectrometers compared to their uncorrected reflectance spectra. All single spectrometer models predicted SOC reasonably well. However, the spectra acquired by the FOSS setup predicted SOC more accurately (R2 = 0.77 and SD = 0.04) than the spectra acquired by the other setups. The models derived from merged uncorrected reflectance spectra yielded poor results (R2 = 0.48 and SD = 0.10); nevertheless, assessment of SOC using the 1st derivative ISS-corrected merged SSLs considerably improved the prediction accuracy (R2 = 0.70 and SD = 0.06). Hence, the derivative spectra coupled with the ISS correction improved the accuracy of SOC prediction models obtained from merged soil spectra collected in different environments using different instruments. We therefore recommend application of the ISS spectral alignment method linked to the 1st derivative approach to enhance the compilation of SSLs at the regional and global scales for SOC assessment.

Kawasaki disease: Clinico-laboratory spectrum and outcome in a cohort of children treated at a tertiary care hospital in Islamabad, Pakistan

Objective: To describe the demographics; clinical, laboratory, echocardiographic findings; treatment and outcome in a cohort of children with Kawasaki disease in a tertiary care hospital. Methods: This is a descriptive, observational, retrospective cohort study conducted at Shifa International Hospital, Islamabad, from January 2013-June 2019. Children who met the criteria for Kawasaki disease according to the American Heart Association and American Academy of Pediatrics guidelines were included. Results: A total of 25 children who met the criteria of Kawasaki disease were included. Their mean age was 43 months (4-150 months). Majority (76%) were males. Eighteen (72%) had complete Kawasaki disease and 7 (28%) had incomplete Kawasaki disease. Fever (> five days) was present in 20 (80%) patients. Eight patients (32%) had echocardiographic changes, out of which two patients (25%) had complete Kawasaki disease and six patients (75%) had incomplete Kawasaki disease. Intravenous immunoglobulin was given to all patients. Fifteen children (60%) received intravenous immunoglobulin within 10 days of fever. None required a second dose. All patients received high dose aspirin at diagnosis which was reduced to antiplatelet dose after resolution of fever for ≥48hrs. Eighteen patients (72%) came for regular follow up. Follow up at 6 months showed complete resolution of echocardiographic changes in six patients (75%), 1 (12.5%) was lost to follow up and one (12.5%) child had persistent coronary artery dilatation. Conclusion: Complete KD was present in 72% of our cohort of children. Coronary artery abnormalities were present in one third of these children, at younger age and more common in those with incomplete KD but recovered in most. doi: https://doi.org/10.12669/pjms.36.2.910 How to cite this:Sakina S, Owais SS, Khan EA, Sheikh AM. Kawasaki disease: Clinico-laboratory spectrum & outcome in a cohort of children treated at a tertiary care hospital in Islamabad, Pakistan. Pak J Med Sci. 2020;36(2):---------. doi: https://doi.org/10.12669/pjms.36.2.910 This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.