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Utilidade da percentagem de eritrócitos hipocrómicos para a avaliação da deficiência de ferro em doentes hemodialisados
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As principais complicações da doença renal crónica (DRC) são desnutrição, acidose metabólica, alteração do metabolismo mineral e anemia. A anemia tem como principais causas, nestes doentes, a deficiência de eritropoietina (devido à própria disfunção renal) e a deficiência de ferro (por redução da ingestão e da absorção intestinal, perdas sanguíneas e inflamação crónica). Sendo um fator que contribui para a progressão da DRC, a sua monitorização e correção são objetivos importantes. Uma vez que baixos valores de ferro podem ser responsáveis por uma fraca resposta aos agentes estimuladores da eritropoiese, a sua monitorização durante a terapia é essencial. Igualmente essencial é a existência de critérios para decisão sobre a administração de suplementos de ferro, orais ou endovenosos. Mas, nos doentes com DRC, sobretudo nos hemodialisados, os valores de ferritina têm pouca sensibilidade para a deficiência de ferro, mesmo para valores mínimos (100 μg/l) substancialmente mais altos do que os usados para a população geral (15 μg/l), dado estes doentes terem frequentemente processos inflamatórios associados. É neste contexto que a percentagem de eritrócitos hipocrómicos (concentração de hemoglobina globular <28 g/dl) pode representar uma mais-valia, uma vez que se correlaciona diretamente com a quantidade de ferro presente na medula óssea. Os valores mínimos aceitáveis para a percentagem de eritrócitos hipocrómicos nos doentes com DRC em hemodiálise são <10% e os valores-alvo são <2,5%.
O objectivo da dissertação consistiu em analisar, numa população de hemodialisados com dimensão significativa (3841 utentes), a significância estatística de algumas correlações importantes no contexto da monitorização da terapêutica com eritropoietina nos doentes renais crónicos em hemodiálise, correlações essas que podem ser deduzidas do modelo geral proposto para a relação entre todos estes marcadores (eritrócitos hipocrómicos, ferritina, saturação da transferrina e PCR).
Foi efectuada a análise descritiva dos dados, centrada essencialmente nas distribuições de frequências (frequência absoluta e relativa), em medidas de tendência central (médias) e em medidas de dispersão (desvio padrão), para cada variável. Para testar a associação entre as variáveis utilizou-se o teste ANOVA one way, Kolmogorov-Smirnoy, Shapiro-Wilk, Teste de Levene para igualdade de variâncias, Teste-t para igualdade de médias e a Correlação de Pearson, (IC 95%, p≤0,05).
Os resultados obtidos demostraram que há uma clara associação entre % de eritrócitos hipocrómicos aumentadas e deficiência de ferro (evidenciada por valores de ferritina < 200 ng/ml).
Por outro lado, valores de ferritina geralmente indicativos de reservas normais de ferro (superiores a 200 ng/ml) tanto se associam a % de eritrócitos hipocrómicos normais como a % de eritrócitos hipocrómicos aumentadas, sendo que os valores de saturação da transferrina corroboram que o último grupo corresponde de facto a situações de deficiência de ferro para a hematopoiese.
The main complications of chronic kidney disease (CKD) are malnutrition, metabolic acidosis, altered mineral metabolism and anemia. Anemia is primarily caused by erythropoietin deficiency (due to renal dysfunction) and iron deficiency (reduced intake and intestinal absorption, blood loss and chronic inflammation). As a contributing factor to the progression of CKD, it’s monitoring and correction are important goals. Since low iron values may be responsible for poor response to erythropoiesis-stimulating agents, their monitoring during therapy is essential. Equally essential is the existence of criteria for decision on the administration of iron supplements, oral or intravenous. However, in patients with CKD, especially in hemodialysis, ferritin values are poorly sensitive to iron deficiency, even at a significantly higher minimum (100 μg/ L) than those used in the general population (15 μg/l), since these patients often have associated inflammatory processes. In this context, the percentage of hypochromic erythrocytes (globular hemoglobin concentration <28 g/dl) may represent an added value, since it correlates directly with the amount of iron present in the bone marrow. The minimum acceptable values for the percentage of hypochromic erythrocytes in CKD patients on hemodialysis are <10% and target values are <2.5%. The aim of this dissertation was to analyze the statistical significance of some important correlations in the monitoring of erythropoietin therapy in chronic renal hemodialysis patients in a hemodialysis population with a significant dimension (3841 users), which can be deduced from the model proposed for the relationship between all these markers (hypochromic erythrocytes, ferritin, transferrin saturation and CRP). The Descriptive analysis of the data was performed, focusing essentially on frequency distributions (absolute and relative frequency), central tendency measures (means) and dispersion measures (standard deviation) for each variable. To test the association between the variables we used the ANOVA one-way test, Kolmogorov-Smirnoy, Shapiro-Wilk and the Levene test for equality of variances and the t-test for equality of means and Pearson's correlation (95% CI, p ≤0.05). The results showed that there is a clear association between increased percentage of hypochromic erythrocytes and iron deficiency (evidenced by ferritin values <200 ng / ml). On the other hand, ferritin values, generally indicative of normal iron stores (greater than 200 ng / ml, are associated with both normal percentage of hypochromic erythrocytes and the increased percentage of hypochromic erythrocytes. Transferrin saturation values corroborate that the latest group corresponds in fact to situations of iron deficiency for hematopoiesis.
The main complications of chronic kidney disease (CKD) are malnutrition, metabolic acidosis, altered mineral metabolism and anemia. Anemia is primarily caused by erythropoietin deficiency (due to renal dysfunction) and iron deficiency (reduced intake and intestinal absorption, blood loss and chronic inflammation). As a contributing factor to the progression of CKD, it’s monitoring and correction are important goals. Since low iron values may be responsible for poor response to erythropoiesis-stimulating agents, their monitoring during therapy is essential. Equally essential is the existence of criteria for decision on the administration of iron supplements, oral or intravenous. However, in patients with CKD, especially in hemodialysis, ferritin values are poorly sensitive to iron deficiency, even at a significantly higher minimum (100 μg/ L) than those used in the general population (15 μg/l), since these patients often have associated inflammatory processes. In this context, the percentage of hypochromic erythrocytes (globular hemoglobin concentration <28 g/dl) may represent an added value, since it correlates directly with the amount of iron present in the bone marrow. The minimum acceptable values for the percentage of hypochromic erythrocytes in CKD patients on hemodialysis are <10% and target values are <2.5%. The aim of this dissertation was to analyze the statistical significance of some important correlations in the monitoring of erythropoietin therapy in chronic renal hemodialysis patients in a hemodialysis population with a significant dimension (3841 users), which can be deduced from the model proposed for the relationship between all these markers (hypochromic erythrocytes, ferritin, transferrin saturation and CRP). The Descriptive analysis of the data was performed, focusing essentially on frequency distributions (absolute and relative frequency), central tendency measures (means) and dispersion measures (standard deviation) for each variable. To test the association between the variables we used the ANOVA one-way test, Kolmogorov-Smirnoy, Shapiro-Wilk and the Levene test for equality of variances and the t-test for equality of means and Pearson's correlation (95% CI, p ≤0.05). The results showed that there is a clear association between increased percentage of hypochromic erythrocytes and iron deficiency (evidenced by ferritin values <200 ng / ml). On the other hand, ferritin values, generally indicative of normal iron stores (greater than 200 ng / ml, are associated with both normal percentage of hypochromic erythrocytes and the increased percentage of hypochromic erythrocytes. Transferrin saturation values corroborate that the latest group corresponds in fact to situations of iron deficiency for hematopoiesis.
Descrição
Palavras-chave
Ciências biomédicas Biologia molecular Doença renal crónica Anemia ferropénica Ferritina Eritrócitos hipocrómicos
Contexto Educativo
Citação
Editora
Instituto de Higiene e Medicina Tropical