Comparison of glucose measurement on dried blood spots versus plasma samples in pregnant women with and without anemia

ABSTRACT Objective Compare the concordance degree between plasma glucose and glucose measurements on Dried Blood Spots (DBS) during pregnancy. Subjects and methods Glucose measurement was performed in pregnant women after a fast of 8-12 hours. Venous blood was collected with sodium fluoride, the plasma was separated, and glucose measured by the enzymatic oxidase glucose method. Capillary blood samples were collected and analyzed by DBS. For statistics, the paired Student's t test, interclass correlation coefficient (ICC), graphic approach of Altman and Bland, and survival - concordance plot were used. Results 307 pregnant women were evaluated, 88.6% without diabetes and 11.4% with previous diabetes. The glucose ranged from 66 to 190 mg/dL [3.66 to 10.55 mmol/L] in plasma and from 53 to 166 mg/dL [2.94 to 9.21 mmol/L] in DBS. The glucose average values were 88.1 ± 12 mg/dL [4.98 ± 0.67 mmol/L] in plasma and 89.2 ±11,5 mg/dL, [4.95 ± 0.64 mmol/L] in DBS - p-value = 0.084. The ICC value was moderate (0.510), and Pearson's correlation coefficient was r = 0.507 p < 0.001. Altman and Bland's graph showed that difference between the values obtained by both methods is -24.62 to 22.3 mg/dL [-1.37 to 1.24 mmol/L]. Significant fixed bias (-1,16 average difference) and proportional bias (r = 0.056; p = 0.33) were not observed. Anemia was associated with differences between plasma glucose and DBS measurements (p = 0.031). Conclusion Capillary glucose in DBS correlates with plasma glucose; however, the methods do not present good concordance. The presence of anemia worsens this result.

Detecção de disfunção renal através da dosagem de creatinina em amostra de gota de sangue seca no papel filtro / Creatinine measurement on dry blood spot sample for chronic kidney disease screening

Resumo Introdução: A identificação precoce da doença renal crônica (DRC) por meio de amostras de sangue e urina é preconizada em populações de risco devido à elevada morbimortalidade. Objetivo: Apresentamos um teste simples e inovador para dosar a creatinina coletada em gota de sangue seca em papel filtro (PF). Métodos: Cento e seis pessoas em risco de DRC foram rastreadas com avaliação de dados clínicos, exame físico e coleta de sangue de forma convencional e em PF. Com os dados obtidos, foi estimada a taxa de filtração glomerular (e-TFG). Foi considerado diagnóstico de DRC a e-TFG < 60 ml/min. Resultados: A idade dos participantes foi de 57 ± 12 anos, 78 (73,5%) eram mulheres, 43 brancos (40,5%), 36 pardos (34%) e 27 negros (25,5%). O índice de massa corpórea foi de 29,5 ± 6,9 kg/m2, a pressão arterial sistólica foi de 125 mmHg (120-140 mmHg) e a pressão arterial diastólica de 80 mmHg (70-80 mmHg). A sensibilidade pela equação CKD-EPI foi de 94%, a especificidade 55%, o valor preditivo positivo foi de 94%, o valor preditivo negativo de 55% e a acurácia de 90%. A estatística de Bland-Altman mostrou que as diferenças entre os valores de creatinina dos dois testes estão numa faixa relativamente estreita (+ 0,68 mg/dL e -0,55mg/dL) para um desvio padrão de ± 1,96 mg/dL. Conclusão: A dosagem da creatinina coletada em gota de sangue em PF é um teste diagnóstico simples de ser realizado, pouco invasivo e que apresentou uma ótima acurácia, podendo ser útil para rastrear DRC.

Abstract Introduction: Chronic kidney disease (CKD) screening is advisable due to its high morbidity and mortality and is usually performed by sampling blood and urine. Objective: Here we present an innovative and simpler method, by measuring creatinine on a dry blood spot on filter paper. Methods: One-hundred and six individuals at high risk for CKD were enrolled. The creatinine values obtained using both tests and the demographic data of each participant allowed us to determinate the eGFR. The adopted cutoff for CKD was an eGFR < 60 ml/min. Results: Mean age was 57 ± 12 years, 74% were female, 40% white, and 60% non-white. Seventy-six percent were hypertensive, 30% diabetic, 37% had family history of CKD, and 22% of smoking. The BMI was 29.5 ± 6.9 kg/m2, median systolic blood pressure was 125 mmHg (IQR 120-140 mmHg) and median diastolic blood pressure was 80 mmHg (IQR 70-80 mmHg). According to MDRD equation, sensitivity was 96%, specificity 55%, predictive positive value 96%, predictive negative value 55% and accuracy 92%. By the CKD-EPI equation the sensitivity was 94%, specificity 55%, predictive positive value 94%, predictive negative value 55% and accuracy 90%. A Bland and Altman analysis showed a relatively narrow range of creatinine values differences (+ 0.68mg/dl to -0.55mg/dl) inside the ± 1.96 SD, without systematic differences. Conclusion: Measurement of creatinine on dry blood sample is an easily feasible non-invasive diagnostic test with good accuracy that may be useful to screen chronic kidney disease.