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L Borque

Publications and source records attributed to L Borque.

33 records · Page 2Linked to original sources
PubMed1993

IgG interference in second generation enzymeimmunoassays for anti-hepatitis C virus antibodies.

The interference of endogenous IgG in the identification of anti-HCV antibodies was studied in three second-generation enzymeimmunoassays. The addition of increasing concentrations of this immunoglobulin led to the appearance of false positives. The results obtained confirm the hypothesis that a non-specific binding of the IgG with the support material used was responsible for this interference.

Evaluation Studies as Topic↗
PubMed1993

Automated turbidimetry of serum lipoprotein(a).

We describe a simple immunoturbidimetric method for quantifying lipoprotein(a) in serum based on latex-enhanced particle agglutination technology. Carboxylated latex particles (diameter 240 nm) covalently coated with F(ab')2 fragments of anti-lipoprotein(a) antibodies are incubated with the sample for 5 min at 37 degrees C, and the resulting agglutination is quantified by measuring the change of turbidity produced at 700 nm. The assay is rapid, precise and fully automated on the Hitachi 911 analyser. The assay range is about 0.03-0.9 g/l. Average analytical recovery was 97.8%. Precision (CV) ranged from 1.9 to 3.1% at different lipoprotein(a) values. There was no interference from bilirubin, Intralipid, haemoglobin, plasminogen or apolipoprotein B. Comparisons with a latex nephelometric assay carried out on the Behring nephelometer analyser, and with three commercially available methods, a radioimmunoassay and two ELISA assays, gave good correlations (r > 0.95), although a large among-method variation in lipoprotein(a) values was found. We conclude that the proposed latex turbidimetric immunoassay method is suitable for routine use in clinical laboratories.

Apolipoproteins B↗
PubMed1992

Automated quantitative nephelometric latex immunoassay for determining ferritin in human serum.

We describe a rapid and sensitive latex nephelometric immunoassay for quantifying ferritin in human serum. This latex immunoassay procedure uses commercially available ready-for-use reagents [Tina-Quant (a) Ferritin, Boehringer Mannheim] that have a long shelf life. The assay consists of incubating the diluted serum sample (5-fold) for 12 min at room temperature with latex particles covalently coated with anti-ferritin antibodies, and then quantifying the change of light-scatter produced. The assay is fully automated on the Behring nephelometer analyzer with a sampling rate of 150 samples/hour. The method has an analytical range of 3 to 260 micrograms/l. Maximal intra- and inter-assay CVs were 4.0 and 6.2%, respectively. Analytical recoveries ranged from 91.3 to 103.6%. Assay detection limit was less than 3 micrograms/l. Linearity of the test is given throughout the measuring range. There was no interference from bilirubin (up to 340 mumol/l), haemoglobin (up to 7 g/l), or rheumatoid factor (up to 1,100 IU/ml). Turbid and lipemic samples interfere. This interference may be avoided by pretreating these samples prior to assay. Results correlated well with those obtained by an automated ELISA test (r = 0.995) and with those of two commercial RIA methods (r greater than 0.97). This latex nephelometric procedure is a convenient method and represents an interesting alternative to other immunoassays for measuring ferritin in human serum.

Adolescent↗
PubMed1992

Measurement of serum beta 2-microglobulin by a latex nephelometric immunoassay.

A rapid and simple technique for the measurement of beta 2-microglobulin on the Behring nephelometer was developed using a commercially available latex-anti beta 2-microglobulin. This is a fully automated assay and no pretreatment of sample is necessary. An excellent correlation with radioimmunoassay (r = 0.972) and time-resolved fluoroimmunoassay (r = 0.914) was obtained. Haemolysis, lipemia, bilirubin, and rheumatoid factor do not cause interference because of the high dilution of samples and the use of Fab fragments of the antibody. The analytical range extends from 0.6 to 10.7 mg/L. Between-run imprecision (CV) ranged from 6 to 8%.

Adolescent↗
PubMed1992

Automated latex nephelometric immunoassay of theophylline in human serum.

A latex test was adapted for the nephelometric quantitation of theophylline in human serum. The assay is fully automated on the Behring Nephelometer Analyser with a sampling rate of 150 samples per hour. There is no interference from bilirubin (up to 340 mumol/l), haemoglobin (up to 7000 mg/l), Intralipid (up to 5 g/l), or rheumatoid factor (up to 1100 x 10(3) IU/l). The theophylline standard curve extends from 1.25 to 40 mg/l. The coefficient of variation ranged from 2.4 to 7.4%. The correlation coefficient between the latex immunoassay and the TDx theophylline procedure was 0.988, calculated from the assay of 74 samples.

Humans↗
PubMed1991

Quantitative automated latex nephelometric immunoassay for determination of myoglobin in human serum.

We have evaluated a new latex nephelometric test for the quantitation of myoglobin in human serum. The assay consists of incubating the diluted serum sample (20-fold) for 12 min at room temperature with latex particles covalently coated with anti-myoglobin antibodies and then quantifying the change of light-scatter produced. The assay is fully automated on the Behring nephelometer analyzer with a sampling rate of 150 samples/hour. There is no interference from bilirubin (up to 340 mumol/l), haemoglobin (up to 7,000 mg/l), or rheumatoid factor (up to 1,100 int. units/ml). Myoglobin standard curve extends from 20 to 380 micrograms/l. Assay detection limit lies around 6 micrograms/l. Coefficient of variation ranged from 2.7 to 7.6%. Correlation coefficient between latex immunoassay and an RIA method was 0.987, calculated from the assay of 37 samples. A statistically significant difference was found between the distribution for females and males. The serum level of myoglobin showed an age-dependent variation. Concentrations up to 60 micrograms/l are considered to be normal.

Adolescent↗
PubMed1991

Automated turbidimetry of rheumatoid factor without heat inactivation of serum.

We describe an improved turbidimetric procedure for rheumatoid factor measurement in human serum. Heat-aggregated human IgG is used as antigen. Interference produced by the complement component C1q, which required a previous heat pretreatment of sera, is avoided by the addition of the chemical inhibitor, poly(vinyl sulphonic acid). This inhibitor eliminates C1q interference without affecting the attachment of rheumatoid factor to the Fc part of IgG, thus permitting full automation of the assay. After studying the reactivity of different heat-aggregated IgG preparations, we optimized the procedure for preparing the antigen in order to attain maximal reactivity: IgG was heated at 63 degrees C until the absorbance at 340 nm of a 1/10 dilution of the antigen lay between 0.65 and 0.95 absorbance units. The study of antigen stability showed a maximum aggregation two weeks after preparation. The antigen was then stable and could be used in the assay. The standard curve extends from 30 to 500 x 10(3) IU/l. Intra- and inter-assay CV were less than 5.5%. Relative analytical sensitivity and specificity were 98.3% and 95.2%, respectively. The results agreed well with those obtained by the non-improved turbidimetric procedure (r = 0.996) and with nephelometry values on the Behring nephelometer analyser (r = 0.964). The correlation with an enzyme immunoassay was also good (r = 0.923).

Complement C1q↗
PubMed1989

Immunoassay by particle counting for coagulation testing: application to the determination of antithrombin III, von Willebrand factor antigen (vWF:Ag) and plasminogen.

Based on immunoassay by particle counting, three methods for antithrombin III, von Willebrand factor and plasminogen were developed on an automated IMPACT machine and on a semi-automated MULTIPACT system. Precision of the techniques, measured at low, medium and high level of the calibration curve showed coefficients of variation varying from 4.3 to 13.8%. Accuracy was evaluated by dilution recovery test and by correlation with rocket immunoelectrophoresis and chromogenic substrate techniques. The results show that the proposed methods correlate well with existing techniques and that immunoassay by particle counting is applicable to several coagulation tests.

Antigens↗
PubMed1986

Turbidimetry of rheumatoid factor in serum with a centrifugal analyzer.

We describe the simple, rapid turbidimetry of IgM rheumatoid factor in human serum by use of the Cobas-Bio centrifugal analyzer. Heat-aggregated human IgG is used as the antigen. The immunoturbidimetric reaction is monitored at 340 nm for 300 s, and the changes in absorbance after the antigen is added are used to prepare the standard curve. Test results are calculated from the stored curve and reported in int. units/mL, based on comparison with the WHO reference serum for rheumatoid factor. There is no interference from bilirubin (up to 340 mumol/L) or hemoglobin (up to 5600 mg/L). Serum samples with a triglyceride concentration greater than 2.20 mmol/L must be cleared of lipids before analysis. The standard curve is linear from 30 to 500 int. units/mL. Precision, accuracy, linearity, and sensitivity are quite acceptable. The CV was generally less than 5% for different concentrations of rheumatoid factor. Results agree well with those by a rate-nephelometric procedure on the Beckman ICS system (rs = 0.932). However, both correlate poorly with a modified classical Waaler-Rose test. Of 47 patients with rheumatoid arthritis, 34 had IgM rheumatoid factor in their serum, but the measured value did not reflect the activity of the disease.

Adult↗
PubMed1983

Rapid turbidimetric determination of serum C3c and C4 by end point centrifugal analysis.

An end point turbidimetric method for the determination of C3c and C4 in serum using a centrifugal analyzer (Cobas Bio) is described. Several analytical factors were evaluated -pH, temperature, PEG and antibody concentration. Wide variations of temperature and pH did not significantly affect the turbidimetric reaction. A 20 g/L PEG concentration and 25-fold antiserum dilution were found satisfactory for the analysis. Precision of the assay was good and comparison with a RID method yielded an r value of 0.97. The procedure is simple and reliable.

Centrifugation↗
PubMedDate not supplied

Rheumatoid arthritis and hepatitis C virus antibodies.

The prevalence of antibodies against the hepatitis C virus (anti-HCV) in patients seropositive for rheumatoid arthritis (RA) and suffering from this disease has been analyzed in comparison to a control group. Our results suggest that the high rate of prevalence found in RA patients is due to IgG interference in the measuring method used.

Arthritis, Rheumatoid↗
PubMedDate not supplied

[Lymphocyte subpopulations, neopterin, and beta-2-microglobulin: relationship with clinical stage, risk of progression to AIDS and presence of active infection in HIV infection].

BACKGROUND: The aim of the present study was to evaluate the relation between the number of CD4 lymphocytes, the CD4/CD8 ratio and the plasma levels of neopterin and beta-2 microglobulin, and the clinical status, risk of progression without of active opportunistic infections, among HIV-infected patients. METHODS: Seventy-two patients infected by HIV in different clinical groups were evaluated upon entering the study and following a mean follow up of 6 months for the parameters studied. RESULTS: The values of CD4 lymphocytes and neopterin were related with the clinical status according to the CDC's classification, with no significant differences existing in the beta-2 microglobulin level. The CD4 count as well as the neopterin and the beta-2 microglobulin levels differed significantly when classified to the patients with regard to the risk of progression to AIDS throughout the study. The presence of active opportunistic infections was related with significantly higher concentrations of neopterin without differences recorded for the remaining parameters. CONCLUSIONS: The parameters studied are good markers or both clinical status and/or the risk of short-term progression to AIDS. Neopterin levels are high during acute infections. Therefore, its prognostic value should be cautiously evaluated in this situation.

Acquired Immunodeficiency Syndrome↗