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Neuroborrelios (NB) kan förekomma när Borrelia garinii, som är en del av artkomplexet Borrelia burgdorferi sensu lato (s.l), infekterar nervsystemet. När immuncellerna utsätts för borreliaantigen bildas antikroppar i plasma och intratekalt. NB ger även upphov till mononukleär pleocytos i cerebrospinalvätska (CSV). Neurologiska symptom, pleocytos och antikroppsindex (AI), som indikerar intratekal syntes av borreliaantikroppar, vägleder nuvarande NB-diagnostik på Klinisk Mikrobiologi i Kalmar. Diagnostiken försvåras vid tidig NB när AI är negativ och pleocytos positiv. För att komplettera tidig NB-diagnostik kan kemokinet C-X-C motif ligand 13 (CXCL13) mätas i CSV. I nuläget utförs CXCL13 enzymkopplad immunadsorberande analys (ELISA) på ett externt laboratorium. Mätning av CXCL13 kan även utföras med en snabb semi-kvantitativ ReaScan+ CXCL13 metod som bygger på lateral flödesimmunanalys (LFIA). Syftet var att verifiera ReaScan+ CXCL13, kontrollera linjäritet, CXCL13 stabilitet och bestämma diagnostisk specificitet och sensitivitet. CSV-proverna indelades i fyra grupper baserat på pleocytos och AI samt tre kategorier utifrån kriterier till NB-diagnos (n=31). Metodjämförelsen genomfördes mellan ReaScan+ LFIA och CXCL13 ELISA (n=25). Linjäritetsanalys utfördes på prov med hög CXCL13-koncentration i CSV och CXCL13-stabiliteten kontrollerades på två patientprover vid frys- och kylförvaring. Beräkning av sensitivitet och specificitet baserades på definitiv (n=20) och ej NB (n=5). Metodjämförelsen visade en fullständig överensstämmelse och Spearman´s korrelationskoefficienten var 0,949. Determinationskoefficienten för linjäritetsanalysen var 0,963. Diagnostisk sensitivitet var 80% och specificitet 100%. Hög prestanda, acceptabla stabilitets- och linjäritetsresultat samt ReaScan+ potentiella förmågan att särskilja mellan definitiv och ej NB, indikerar att metoden kan införas på Klinisk Mikrobiologi i Kalmar och komplettera nuvarande diagnostik av tidig NB. / Lyme neuroborreliosis (LNB) occurs when Borrelia garinii, part of the Borrelia burgdorferi sensu lato (s.l) species complex, infects the nervous system. Upon exposure, immune cells produce antibodies that can be measured in serum or cerebrospinal fluid (CSF). LNB also cause mononuclear pleocytosis in CSF. Neurological symptoms, pleocytosis and antibody index (AI), which indicate intrathecal synthesis of Borrelia antibodies, guide current diagnosis of LNB at the Clinical Microbiology in Kalmar. The diagnosis is complex in early LNB, especially when AI is negative and pleocytosis is positive. Expression of chemokine C-X-C motif ligand 13 (CXCL13) in CSF can be used as an additional marker to early LNB. Analysis is currently performed at an external laboratory using enzyme-linked immunosorbent assay (ELISA). The aim of this project was to evaluate the performance of the rapid semi-quantitative lateral flow immunoassay (LFIA) ReaScan+ CXCL13 test using 31 patient samples divided into four groups based on pleocytosis and AI. Linearity assay was performed on samples with high CXCL13 concentrations and stability was tested on two CSF samples after freezing and refrigeration. Estimation of sensitivity and specificity was based on definite (n=20) and non-LNB (n=5). Method comparison showed a complete agreement and Spearman's correlation coefficient was 0,949. The R2 for linearity was 0,963. Sensitivity was 80% and specificity 100%. Strong agreement, acceptable stability and linearity results as well as ReaScan+ potential ability to distinguish between definite and non-NB, indicate that the method can be introduced at Clinical Microbiology in Kalmar and used as a supplement in early LNB diagnostics.

Paper strips are becoming widely used for blood testing and particularly with embedded immunoassays. Among the so called "Point of Care" devices, the association of LFIA tests with a reading technology able to capture the strip and analyze its composition to output the biological result is advantageous in many ways.         In this thesis, a biosensor composed of a LFIA strip embedded on a reading device is investigated. The variability of the optical system used in the device is assessed, and the dynamic of the capillary flow in the LFIA strip is investigated in order to build a model of the flow field to understand the test physically and further optimize it.         Statistical methods based on available database as well as experimental data are used in order to assess the optical system variability. The camera variability in positioning, zoom and sharpness is investigated, as well as LED lightning system reproducibility and repeatability. The camera shows a zoom variability of 6% when computed on the database of devices available, and around 40% for sharpness variability. It reveals that sharpness is the most sensible camera parameter, because images of different sharpness gives varying results in the signal processing measurement method used to output the biological result. The lightning system has a variability below 1%, a reproducibility of 4%, and a repeatability below 1%, which are low results and it comforts the reliability of the lightning system during the measurement process. The different quantitative results for the optical system performances give precious insight on the further signal processing methods used to analyze the strip composition.         The paper strip is composed of four different substrips placed horizontally in series with different length and cross section. The method consists in setting up a model for the flow field by combining Darcy's law and mass conservation at the junction between strips. A relation between the fluid velocity and travelling distance is deduced. The four paper parameters are determined experimentally and input into the model equations. The flow field model fits favorably to experimental result of the flow in the strip. The model presents velocity jumps at the junction between strips and the importance of paper parameters such as cross sections, porosity, permeability and capillary pressure to govern the flow field is stressed. The flow field microfluidic model demonstrates that Darcy's law has to be modified in order to account for the pad superposition.         This project lead to a quantification of optical system variability sources which help choosing the signal processing methods embedded in the software to read and analyse the LFIA strip test. They will also be further used for designing device quality tests to ensure that the device is able to output a reliable biological result. The microfluidic model built and combined with experimental flow data helps to understand and optimize the flow in the strip, which is responsible for bringing the analyte of interest towards the reaction zone on the strip. This model could be enhanced if linked to the biochemical reaction kinetic model, and could further be integrated into a more general biosensor model to predict its behavior physically and biologically.