Diagnostic performance of the loop-mediated isothermal amplification (LAMP) based illumigene® malaria assay in a non-endemic region.

BACKGROUND: Light microscopy and antigen-based rapid diagnostic tests are the primary diagnostic tools for detecting malaria, although being labour-intensive and frequently challenged by lack of personnel's experience and low levels of parasite density. The latter being especially important in non-endemic settings. Novel molecular techniques aim to overcome this drawback. The objective of this study was to assess the diagnostic performance of the illumigene malaria assay® (Meridian Bioscience) compared to microscopy, RDT and real-time PCR. This loop-mediated isothermal amplification (LAMP) assay is a qualitative in vitro diagnostic test for the direct detection of Plasmodium spp. DNA in human venous whole blood samples. METHODS: The illumigene assay was assessed on a retrospective panel of stored blood samples (n = 103) from returned travellers and external quality control samples (n = 12). Additionally the assay was prospectively assessed on 30 fresh routine samples with a request for malaria diagnosis. The illumigene assay was compared to microscopy, RDT and Plasmodium species specific real-time PCR. RESULTS: In the retrospective evaluation, the illumigene assay showed 100% agreement with the real-time PCR, RDT and microscopy yielding a sensitivity and specificity of 100% (95% CI 95.1-100% and 89.7-100%, respectively). Seven samples from patients recently treated for Plasmodium falciparum infection that were RDT positive and microscopy negative yielded positive test results. The performance of the illumigene assay equals that of microscopy combined with RDT in the prospective panel with three false negative RDT results and one false negative microscopy result. Excellent concordance with PCR was observed. The limit of detection of the assay approached 0.5 parasites/µL for both P. falciparum and Plasmodium vivax. CONCLUSION: In non-endemic regions where the diagnostic process for malaria infections is questioned by lack of experience and low levels of parasite densities, the illumigene assay can be of value. Due to its high sensitivity, the LAMP assay may be considered as primary diagnostic test. The results of this study indicate that negative screen results do not need further confirmation. However, before implementation, this approach needs to be confirmed in larger, prospective studies. A shortcoming of this assay is that no species identification nor determination of parasite density are possible.

Detailed faecal fat analysis using Fourier transform infrared spectroscopy: Exploring the possibilities.

OBJECTIVES: Fourier transform infrared (FTIR) spectroscopic determination of faecal fat is a simple and elegant alternative for the classical Van De Kamer approach. Besides quantification of the total amount of fat, analysis of the lipase hydrolysis efficiency (fatty acid/triglyceride ratio), fatty acid chain length and trans-unsaturated fatty acids could provide a better monitoring of dietary treatment. DESIGN AND METHODS: Stool samples (26 routine samples and 36 cystic fibrosis patients) were analysed with the Perkin Elmer Spectrum Two® spectrometer (3500-450cm-1). Fatty acid/triglyceride ratio was calculated using the absorbance ratio at 2855:1746cm-1. To estimate lipase hydrolysis efficiency, sample ratios were compared with the ratio of butter and pure free fatty acids. Mean fatty acid chain length was calculated using the absorbance ratio at 2855:1709cm-1. The absorbance at 966cm-1 was used to trace the presence of trans-type unsaturated fatty acids. RESULTS: Butter showed a low fatty acid/triglyceride ratio (1.21) and pure free fatty acids a high fatty acid/triglyceride ratio (6.76). Mean fatty acid/triglyceride ratio of routine stool samples was 4.16±1.01. The applicability of fatty acid/triglyceride ratios was also tested in cystic fibrosis patients under treatment with a mean of 4.92±0.98. Relative absorbance contribution per carbon atom was 0.06 (ratio 1.06 for C18 standard, 0.91 for C16 standard). The mean ratio of the stool samples was 1.12 (mean acyl chain length of C19), with values ranging from 0.73 (C12) to 1.68 (C28). The presence of traceable amounts of trans-unsaturated fatty acids was also demonstrated. CONCLUSIONS: For the analysis of faecal material, FTIR provides unique information, difficult to obtain using other techniques. These findings offer perspectives for diet monitoring in patients with (non-)pancreatic malabsorption.

An Unusual Type of Kidney Stone.

A very rare case of acetylsulfapyridine nephrolithiasis is presented in a 54-year-old female patient who had been prescribed sulfasalazine (6 x 500 mg/day) because of psoriatic arthritis for the last 9 years. The patient's renal function was only slightly impaired. Reflectance infrared spectroscopy and gas chromatography-mass spectrometry allowed the identification of the chemical nature of the stone. As acetylsulfapyridine is a metabolite of sulfasalazine, administration of the latter drug was the cause of the nephrolithiasis.

Analytical performance evaluation of four cartridge-type blood gas analyzers.

BACKGROUND: The immediate impact of blood gas test results on patient care favors the use of blood gas analyzers as point-of-care-testing (POCT) devices. We performed an analytical performance evaluation of four cartridge-type blood gas analyzers for the determination of pH, partial carbon dioxide pressure (pCO2), partial oxygen pressure (pO2), ionized calcium (iCa2+), potassium (K+), glucose, lactate and total hemoglobin (tHb), in comparison with a traditional blood gas analyzer. METHODS: The analyzers included in the study are: RP405, GEM Premier 4000, ABL90 FLEX and Cobas b 123. The ABL700 served as comparator. For each instrument the imprecision was estimated according to the CLSI EP5-A2. Based on the CLSI EP9-A2 evaluation protocol, a method comparison was performed using patient samples. Obtained data were compared against preset quality specifications, based on ABL700 performance and biological variation. RESULTS: The precision of the RP405 and ABL90 FLEX was remarkably better than the preset criteria based on ABL700 performance. The GEM appears to have the worst precision. The RP405 yielded the best overall performance, with exception for tHb and iCa2+. Noteworthy is the very good performance of the glucose determination on RP405. The ABL90 FLEX showed the best performance for pH, K+ and iCa2+ measurements. For tHb determination the Cobas b123 revealed the best results. Regarding practicability, all instruments were found to be user friendly. CONCLUSIONS: Globally, all four cartridge-type blood gas analyzers produced clinically acceptable results. The analytical performance, together with the ease of use and low maintenance time of the instruments, demonstrate that these analyzers are perfectly suitable for both POCT and laboratory use.