Camila Cardoso de Oliveira

Statistical Approaches to Assess the Association between Phenolic Compounds and the in vitro Antioxidant Activity of Camellia sinensis and Ilex paraguariensis Teas.

Tea presents a diverse phenolic composition which is responsible for its alleged biological activities, including the in vivo and in vitro antioxidant capacity. It is very usual to find researches applying univariate/bivariate statistical methods, such as analysis of variances (ANOVA) and linear Pearson correlation coefficients to analyze the strength of correlation between phenolic composition and the in vitro antioxidant activity of teas from Camellia sinensis (green, black, white, oolong, red, and yellow teas) and Ilex paraguariensis (Yerba-mate), which are the most produced and consumed types of teas. However, evidence has shown that these approaches are not as suitable as multivariate statistical methods once they do not depict nor show association among all results and variables simultaneously, making it difficult to understand clearly the data structure and patterns. Then, the objective of this work is to review and explain some univariate/bivariate and multivariate statistical techniques used to assess the association between phenolic compounds and the in vitro antioxidant activity of green, white, black, red, yellow, oolong and Yerba-mate teas. Moreover, this paper provides an overview on some assays used to estimate the in vitro antioxidant capacity of teas.

Estabilidade dos soros para o controle de qualidade interno de testes imunodiagnósticos de HIV/AIDS

Introduction: The use of reference materials in order to assure and perform the quality control of analytical measurements is a requirement in clinical laboratories. Objectives: Stability of serum samples, kept frozen at -20°C for long-term storage and at varied temperatures during short periods, was evaluated by investigating the persistency of anti-human immunodeficiency virus (HIV) antibodies reactivity on enzyme-linked immunosorbent assay/enzyme immunoassay (ELISA/EIA), Western blot and indirect immunofluorescence assays. Method: The analyzed sera were part of serum panels (comprised of anti-HIV positive and negative samples), produced at the Immunology Center of Instituto Adolfo Lutz, which have been the reference specimens for producing the internal quality assurance sera of HIV/acquired immunodeficiency syndrome (AIDS) immunodiagnostic assays. Sera stability was assessed in samples stored at -20°C for 56 weeks, and at various temperature conditions: from 2°C to 8°C (refrigerator), from 15°C to 25°C (room temperature), at 37°C (incubator) and at -80°C (freezer) for 24 and 48 hours. The statistical analyses on HIV-negative serum samples (long-term storage) were significant (p < 0.05), and neither adverse effects on these samples as the occurrence of false-positive results nor false-negative results in HIV antibody positive sera were found in both studies. Conclusion: It was possible to conclude that the reference material remained stable for 48 hours at different temperatures (short-term) and it remained stable at -20°C for 56 weeks (long-term).

Homogeneity study of the internal quality control sera for immunodiagnosis of HIV/AIDS

Introduction: The present study reports the data from the first homogeneity assessment of samples composing the serum panels produced at the Immunology Center of Instituto Adolfo Lutz, Sao Paulo. These samples have been distributed to the public laboratories and those partaking in the Brazilian Unified Health System, and to the participants in the Internal Quality Control Program for human immunodeficiency virus (HIV) antibody (Ab) testing. Objective: To assess the homogeneity of serum samples in panels from different lots for HIV/acquired immunodeficiency syndrome (AIDS) immunodiagnosis by using the statistical method to ensure quality of the reference material. Method: Sera homogeneity was evaluated by means of enzyme-linked immunoassay/enzyme immunoassay (ELISA/EIA) for detection of HIV Ab, and the one-way analysis of variance was employed for analyzing the data. No statistically significant differences were found among the several serum vials. Conclusion: The sera dispensed in the vials were homogeneous in the respective lots.

Study on the stability of HIV and syphilis reference materials under varied temperature conditions during their transportation

Introduction: The objective of this study was to evaluate the short-term stability of the serum samples used as internal quality control (IQC) of human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (Aids) and syphilis immunodiagnostic assays. These samples were produced at the Center of Immunology-Instituto Adolfo Lutz (IAL), and they were distributed to laboratories participating in the IAL Quality Control Program. Method: The sera analyzed by chemiluminescence assay were stored at varied temperature conditions: from 2oC to 8oC (refrigerator), from 15oC to 25oC (room temperature), at 37oC (incubator) and at -20oC (reference temperature) for 12 and 24 hours. Results: Comparative analysis of IQC results for anti-HIV and anti-T. pallidum (anti-treponemal) showed stability in the reference temperature and at the various simulated temperatures for transporting the samples at the established lengths of time. The data from the simple linear regression analysis of negative serum samples (incubator/24 hours) and in one batch of HIV IQC (room temperature/24 hours) were statistically significant at the level of 5% (p-value < 0.05). Conclusion: The sera presented necessary requirements as reference material to be transported to laboratories at refrigeration temperature (2oC to 8oC), at the maximum shipping time of 12 hours.

Efeito dos múltiplos ciclos de congelamento e descongelamento na estabilidade de amostras de soro antitreponêmico positivo

Introduction: Biological samples have long been used in multiple laboratory investigations, and this procedure has been an issue of concern, as the samples are submitted to repeated freeze-thaw cycles, which may affect the results of a particular immunodiagnostic assay, due to the occurrence of physical damage to the antibody of interest. Objective: This study aimed at investigating the impact of successive freeze-thaw cycles on the stability of serum samples stored at -20oC regarding the reactivity of anti-treponemal antibodies. Methods: At the Immunology Center-Instituto Adolfo Lutz (IAL), the analyzed serum samples analyzed were prepared and established as reference material for anti-treponemal immunodiagnostic assays. Sera stability was evaluated by chemiluminescence assay in samples submitted to 25 successive freeze-thaw cycles, ranging from 6 to 174 cycles. Results: Neither statistically significant effect on the reactivity of anti-treponemal antibodies (p-value > 0.05), nor adverse effect were observed in weakly reactive samples, such as the occurrence of false-negative results. Conclusion: It was shown that 174 freeze-thaw cycles of anti-treponemal sera did not affect the stability and the quality of samples, when evaluated by chemiluminescence assay.

Influence of distillation time and sample mass on sulfur dioxide analysis in passion fruit juice through Monier-Williams method.

This study aimed to evaluate the effect of the distillation time and the sample mass on the total SO2 content in integral passion fruit juice (Passiflora sp). For the SO2 analysis, a modified version of the Monier-Williams method was used. In this experiment, the distillation time and the sample mass were reduced to half of the values proposed in the original method. The analyses were performed in triplicate for each distilling time x sample mass binomial, making a total of 12 tests, which were performed on the same day. The significance of the effects of the different distillation times and sample mass were evaluated by applying one-factor analysis of variance (ANOVA). For a 95% confidence limit, it was found that the proposed amendments to the distillation time, sample mass, and the interaction between distilling time x sample mass were not significant (p > 0.05) in determining the SO2 content in passion fruit juice. In view of the results that were obtained it was concluded that for integral passion fruit juice it was possible to reduce the distillation time and the sample mass in determining the SO2 content by the Monier-Williams method without affecting the result.

Avaliação de limite de decisão (CCa) e capacidade de detecção (CCb) a partir de curvas analíticas em análises de águas para substânciascom teores permitidos: uma planilha eletrônica para a interpretaçãode resultados em Laboratórios de Saúde Pública

In this paper the electronic spreadsheets built in Microsoft ExcelR software are presented, and these parameters enable to estimate the decision limit (CCα) and the detection capability (CCβ) at the detection limit and of the maximum permitted value (MVP) regions. The estimates are evaluated from linear and homoscedastic analytical curves obtained in calibration procedures based on ISO standards and IUPAC guidelines. After validating by means of manual data processing, the electronic spreadsheets were used for determining the nitrite in bottled waters (MVP = 0.02 mg/L) and the fluoride contents in public supply waters (compliance interval = 0.6 to 0.8 mg/L). For fluoride analysis there are the minimum required value (0.6 mg/L) and the maximum acceptable value (0.8 mg/L) for its concentration; therefore, the spreadsheet computes the critical concentration at both limits with a probability of a type I error equal to 0.05. On that account, the electronic spreadsheets provide the rapid decision between compliant and non-compliant data in the interpretation of results.

Comparação de diferentes métodos estatísticos utilizados para avaliar o desempenho de participantes em um programa de ensaio de proficiência

Five statistical approaches were applied for assessing the performance of participants in 19 rounds (2007-2011) of the Proficiency Testing Program for lead in blood determination (PEP-Pbs), conducted by Instituto Adolfo Lutz. The performance evaluation was provided by using the z-score. The following statistical approaches were tested: 1 – mean and standard deviation, after rejecting outliers; 2 – median and normalized inter-quartile range; 3 – robust mean and robust standard deviation; 4 – robust mean and standard deviation for proficiency assessment of 3 μg/100 mL (for concentrations up to 40 μg/100 mL and a standard deviation for proficiency assessment of 7.5 % of the assigned value (for concentrations above 40 μg/100 mL); 5 – robust mean and standard deviation for proficiency assessment of 2 μg/100 mL (for concentration up to 40 μg/100 mL) or 5 % of the assigned value (for concentrations above 40 μg/100 mL). The approach 4 showed to be the most adequate statistical methodology to assess the performance of participating laboratories in the PEP-Pbs.Five statistical approaches were applied for assessing the performance of participants in 19 rounds (2007-2011) of the Proficiency Testing Program for lead in blood determination (PEP-Pbs), conducted by Instituto Adolfo Lutz. The performance evaluation was provided by using the z-score. The following statistical approaches were tested: 1 – mean and standard deviation, after rejecting outliers; 2 – median and normalized inter-quartile range; 3 – robust mean and robust standard deviation; 4 – robust mean and standard deviation for proficiency assessment of 3 μg/100 mL (for concentrations up to 40 μg/100 mL and a standard deviation for proficiency assessment of 7.5 % of the assigned value (for concentrations above 40 μg/100 mL); 5 – robust mean and standard deviation for proficiency assessment of 2 μg/100 mL (for concentration up to 40 μg/100 mL) or 5 % of the assigned value (for concentrations above 40 μg/100 mL). The approach 4 showed to be the most adequate statistical methodology to assess the performance of participating laboratories in the PEP-Pbs.

Emprego de planilhas eletrônicas, baseadas nas normas ISO e recomendações IUPAC, em curvas analíticas da análise de água

This paper describes the development and validation of the electronic spreadsheet in Microsoft Excel® software for evaluating the analytical quality of calibration graphs of linear and homoscedastic functions, used in water physical-chemical analysis by UV-Vis spectrophotometry, and obtained according to ISO standards and IUPAC guidelines. By introducing the absorbance data, the spreadsheet shows the calibration (with respective function) and the residues graphs, and also computes the residual standard deviation, angular coefficient standard deviation, interception standard deviation, and coefficient of determination R2. On prediction terms, the spreadsheets calculate (confidence level at 95 %): the prediction interval (showing the respective curve with upper and lower limits), the absorbance critical value, the concentration critical value (xC), the minimum detectable value of concentration (xD) or detection limit, the quantification limit, and the confidence intervals for samples. From the initial spreadsheet, simplifications were introduced and the new spreadsheets were used for analyzing nitrate, nitrite and iron. The effect of the simplifications on the parameters calculation, and the correlations between xC/xD ISO 11843-1,2 parameters and the CCα(decision limit)/CCβ(detection capability) European Commission parameters, were discussed. Keywords. analytical quality control, analytical curves, water analysis, electronic spreadsheets.