Dried blood spots: a robust tool for malaria surveillance in countries targeting elimination

With the advancements in analytical and molecular techniques, Dried Blood Spots (DBS) are re-emerging as attractive and cost-effective alternatives for global health surveillance. The use of DBS has been well-characterized in the neonatal screening of metabolic diseases, therapeutic screening as well as in epidemiological studies for biomonitoring. Malaria is one such infectious disease where DBS use can expedite molecular surveillance for assessing drug resistance and for refining drug usage policies. In India, malaria cases have reduced significantly over the past decade but to achieve malaria elimination by 2030, country-wide DBS-based screening should be conducted to identify the presence of molecular markers of artemisinin resistance and to study parasite reservoirs in asymptomatic populations. DBS has wide applications in genomics, proteomics, and metabolomic studies concerning both host and pathogen factors. Hence, it is a comprehensive tool for malaria surveillance that can capture both host and parasite information. In this review, we elucidate the current and prospective role of DBS in malaria surveillance and its applications in studies ranging from genetic epidemiology, parasite and vector surveillance, drug development and polymorphisms to ultimately how they can pave the roadmap for countries aiming malaria elimination

Standardization of an organic DNA extraction method from dried blood spots and its downstream molecular applications in neonatal screening and diagnostic confirmation of lysosomal disorders

Introduction: Dried blood spot (DBS) samples have been used for diagnostic purposes since their introduction in the neonatal screening of phenylketonuria almost 50 years ago. The range of its application has been extended to modern approaches, such as next-generation sequencing (NGS) for molecular genetic testing. This study aimed to evaluate the use of a standardized organic method for DNA extraction from DBS samples in the diagnostic setting.Methods: The clinical applicability of the method was tested using 3 samples collected from a newborn screening project for lysosomal storage diseases, allowing the determination of the genotype of the individuals. DNA was extracted from 3 3-mm diameter DBS punches. Quality, purity, and concentration were determined, and method performance was assessed by standard polymerase chain reaction, restriction length polymorphism, Sanger sequencing, and targeted NGS.Results: Results were compared with the ones obtained from DNA samples extracted following the internally validated in-house extraction protocol that used 6 3-mm punches of DBS and samples extracted from whole blood.Conclusion: This organic method proved to be effective in obtaining high-quality DNA from DBS, being compatible with several downstream molecular applications, in addition to having a lower cost per sample

Alpha-Galactosidase A Levels in Colombian Males with End-Stage Renal Disease: Ten Years of Selective Screening in Dried Blood Spots

Abstract Fabry disease is a metabolic alteration linked to an enzymatic deficiency of Alpha-Galactosidase A, this disorder compromises the sphingolipid metabolism, leading to an accumulation of lysosomal globotriaosylceramide and is inherited in an X-linked recessive way. The diagnostic of this disease, in general, requires the confirmation of below-normal levels of Alpha-Galactosidase A obtained from dried blood spot (DBS) samples, followed by an assessment of the enzyme in leukocytes. We aimed to report the Alpha-Galactosidase A values obtained in Colombian males with end-stage renal disease (ESRD) screened using dried blood spot samples during ten years. This screening was performed with samples sent to the analysis center from 6156 patients between 2006- 2016. All patients with low levels in enzyme activity (compared to the control population) were sent to confirmation through enzyme analysis in isolated leukocytes. 26 males (0.42%) with low levels of Alpha-Galactosidase A were identified (Range 0.0 - 1.14 nmol/ml/hour, cut-off: 1.15), 22 patients were subsequently measured in isolated leukocytes having a confirmation of Fabry disease in 5 patients (0.08% of total male population) (Range: 0.3 -4.7 nmol/mg prot/h). These results are similar to those reported in studies with comparable characteristics being this the first reporting frequency of Fabry disease among Colombian males with end-stage renal disease.

How Long are Residual Newborn Screening Specimens Useful for Retesting when Stored in Suboptimal and Uncontrolled Conditions of Temperature and Humidity?

Abstract Residual DBS specimens from newborns diagnosed with Phenylketonuria, Congenital Hypothyroidism, Cystic Fibrosis, Congenital Adrenal Hyperplasia and Galactosemia collected within 1995-2018, stored in cardboard boxes at ambient temperature in uncontrolled conditions, were retested for phenylalanine (Phe), thyrotropin (TSH), immunoreactive trypsinogen (IRT), total galactose (TGal) and 17-hydroxyprogesterone (17OHP), to demonstrate how long are they stable in these conditions and useful to reconfirm a previous abnormal result. Recovery percentage at retesting and qualitative interpretation regarding the current cutoff were evaluated. Phe, TSH and IRT recoveries showed decreasing trends along time. Phe recovery was 64 % after 2-years storage; TSH decayed rapidly recovering 47.3 % at 1-year, while IRT showed recoveries of 60 % at 1-year. Although 17OHP recovery presented a wide variation of results, a decaying trend was also found. Results suggest 17OHP is more stable than TSH and IRT, as supported by recoveries > 71 % when stored ≤ 2-years. TGal recovery presented an erratic behavior, so that it was not possible to estimate expected concentrations as a function of storage time. TGal recoveries above 100 % were found in UDP-galactose-4-epimerase and galactose-1-phosphate uridyltransferase deficiencies, evidencing possible galactose liberation from other sources. These results make a very valuable contribution for programs storing residual DBS in uncontrolled conditions.

Análisis de beta-glucosidasa en sangre seca recolectada en papel filtro (DBS), reporte de un nuevo método aplicado a población control y pacientes con sospecha de enfermedad de Gaucher / Beta-Glucosidase analysis in collected dried blood spots (DBS), report of a new method applied to the control population and patients with suspicion of Gaucher disease / Análise de β-glucosidase em sangue seco coletado em papel filtro (DBS), relatório de um novo método aplicado à população controle e a pacientes com suspeita de doença de Gaucher

Resumen: La enfermedad de Gaucher (GD) es el trastorno de almacenamiento lisosomal que se caracteriza por la deficiencia en la actividad enzimática de la β-glucosidasa (BGLU), lo que produce la acumulación de glucosilceramida en las células. Su diagnóstico se orienta a la valoración de la enzima en los leucocitos afectados. Se han realizado estudios en DBS para la actividad de BGLU en el seguimiento de poblaciones de alto riesgo; sin embargo, presentan interferencias relacionadas a leucopenias severas o expresión aumentada de la isoforma neutra de la enzima BGLU, molécula no relacionada con GD. El objetivo de este estudio fue la estandarización de un método de tamizaje en DBS (punch: 5 mm) con el uso de 4-metilumbeliferil-β-D-glucósido y conduritol-β-epóxido. Se analizaron muestras de DBS de 395 individuos con sospecha clínica (población de alto riesgo o AR), 151 controles y 16 pacientes afectados, usando la elución de un corte de 5 mm (≈10 μl de sangre) en 300 μl de Tritón X-100/(0,5 %). Como resultados, se obtuvieron los rangos, AR: 0,84-26,92 nmol/ml/h, controles: 3,56- 8,92 nmol/ml/h (M = 5,56, DS = 1,15) y pacientes confirmados con GD: 0,82- 2,88 nmol/ml/h (M = 1,64, DS = 0,57). El punto de corte entre deficientes y controles fue 3,22 nmol/ml/h, obtenido a partir de análisis ROC (99 % confianza, 100 % sensibilidad y 100 % especificidad). El protocolo permitió evidenciar la deficiencia en todos los casos de GD, confirmados mediante el análisis en paralelo de la enzima en aislamiento leucocitario. Se recomienda el uso del CBE y realizar la elución del corte a 5 mm, a fin de llevar a cabo la valoración enzimática con un volumen mayor aproximado de sangre y en ausencia de la actividad generada por la isoforma neutra.

Abstract: Gaucher disease (GD) is a lysosomal storage disorder characterized by a deficiency in the enzymatic activity of β-glucosidase (BGLU), resulting in the accumulation of glucosylceramide in cells. Its diagnosis is aimed at checking the enzyme in the affected leukocytes. Studies have been conducted on dried blood spots (DBS) for bglu activity to monitor high-risk populations; however, they exhibit interferences related to severe leukopenias or increased expression of the neutral bglu isoform, a molecule not related to gd. This study intends to standardize a screening method on dbs (punch: 5 mm) using 4-methylumbelliferyl-β-D-glucoside and conduritol-β-epoxide (CβE). dbs samples from 395 individuals clinically suspected of gd (high-risk or hr population), 151 controls, and 16 affected patients were analyzed using the elution of 5 mm punches (≈10 μl of blood) in 300 μl of Triton X-100/ (0.5 %). As a result, the following ranges were obtained; HR: 0.84-26.92 nmol/ml/h, controls: 3.56-8.92 nmol/ml/h (M = 5.56, SD = 1.15), and patients with confirmed GD: 0.82-2.88 nmol/ml/h (M = 1.64, SD = 0.57). The cut-off point between patients with gd and controls was 3.22 nmol/ml/h, obtained from roc analysis (99 % ci, 100 % sensitivity, and 100 % specificity). The protocol revealed a deficiency in all gd cases, confirmed by parallel bglu analysis in isolated leukocytes. The use of cbe and the elution of 5 mm punches are recommended for enzymatic evaluation with a higher approximate volume of blood and in the absence of neutral isoform activity.

Resumo: A doença de Gaucher (GD) é o trastorno de armazenamento lisosomal caracterizado pela deficiência na atividade enzimática da β-glucosidase (BGLU), o que produz a acumulação de glucossilceramida nas células. Seu diagnóstico está orientado à avaliação da enzima nos leucócitos afetados. Foram realizados estudos em dbs para a atividade de BGLU no seguimento de populações de alto risco; contudo, são apresentadas interferências relacionadas a leucopenias graves ou a expressão aumentada da isoforma neutra da enzima BGLU, molécula não relacionada com GD. O objetivo deste estudo foi a padronização de um método de tamisação emdbs (punch: 5 mm) com o uso de 4-metilumbeliferil-β-D- glicosídeo e conduritol-β-epóxido. Foram analisadas amostras de dbs de 395 indivíduos com suspeita clínica (população de alto risco ou ar), 151 controles e 16 pacientes afetados, usando a eluição de um corte de 5 mm (≈10 μl de sangue) em 300 μl de Tritão X-100/(0,5 %). Como resultados, foram obtidos os intervalos: AR: 0,84-26,92 nmol/ml/h, controles: 3,56-8,92 nmol/ml/h (M = 5,56, DS = 1,15) e pacientes confirmados com GD: 0,82- 2,88 nmol/ml/h (M = 1,64, DS = 0,57). O ponto de corte entre deficientes e controles foi 3,22 nmol/ml/h, obtido a partir de análise ROC (99 % confiança, 100 % sensibilidade e 100 % especificidade). O protocolo permitiu evidenciar a deficiência em todos os casos de GD, confirmados mediante a análise em paralelo da enzima em isolamento leucocitário. É recomendado o uso do cbe e a realização da eluição do corte a 5 mm, a fim de implementar a avaliação enzimática com um volume maior aproximado de sangue e em ausência da atividade gerada pela isoforma neutra.

Evaluation of dried blood spots as a feasible alternative to plasma for the detection and quantification of hepatitis c virus in a tropical setting: A pilot study

Introduction: Confirmatory diagnosis of hepatitis C virus (HCV) infection (HCV RNA detection) is essential before start of the therapy. HCV RNA detection is not available in many parts of India. Shipment of plasma from distant places to referral laboratories may affect HCV RNA titres. Dried blood spots (DBS) provide an easy alternative for transporting samples to centres where HCV RNA testing is done. Aim: Evaluation of DBS as a feasible alternative to plasma for HCV diagnosis. Methods: In this cross-sectional study, 40 consecutive patients' blood samples were collected from patients referred from the Liver Clinic. Whole blood was spotted onto two Whatman 903TM cards. One card was incubated at ?37癈 and other at 4癈 for 15 days, after drying. DBS was eluted and run in Abbott RealTime HCV assay. HCV was also quantified using the Abbott ARCHITECT HCV core antigen assay for 29 of the study patients. Results were compared with normal plasma values. Results: The median log HCV RNA value (in log10IU/mL) of plasma was 5.74, with normalised DBS it was 4.92 (?37癈) and 4.66 (4癈); difference in plasma and DBS median log values was 0.82 (?37癈) and 1.08 (4癈) logs, respectively. Interclass correlation values were 0.943, P < 0.0001 (?37癈) and 0.950, P < 0.0001 (4癈), showing high agreement. The median HCV core antigen value (in fmol/L) for plasma was 325.35, whereas it was 4.77 (?37癈) and 4.64 (4癈) for DBS samples. Conclusions: DBS can be used for sampling patients from distant resource-limited settings as an alternative to plasma for HCV RNA estimation. Larger studies are required to evaluate the feasibility of DBS in the Indian subcontinent, especially for HCV core antigen estimation.

Determination of 25-Dydroxyvitamin D2 and 25-Hydroxyvitamin D3 in Dried Blood Spots Using Liquid Chromatography- Tandem Mass Spectrometry / 分析化学

A high-throughput method is established to determine 25-hydroxyvitamin D2[25(OH)D2] and 25-hydroxyvitamin D3 [ 25(OH)D3 ] in dried blood spots ( DBS ) by liquid chromatography-tandem mass spectrometry ( LC-MS/MS) , which only needs a DBS sample prepared from about 6 μL of whole blood. The DBS sample processing includes ultrasonic extraction of analytes, addition of 25(OH)D2-D6 and 25(OH)D3-D3 as internal standard, application of 4-phenyl-1, 2, 4-triazoline-3, 5-dione ( PTAD ) as derivatization reagent. The procedure is carried out in a 96-well plate format in an automated liquid handling platform to facilitate high-throughput analysis. The processed sample is separated in a C18 column with water-methanol gradient elution, and quantitated by mass spectrometry in multiple reaction monitoring ( MRM) mode. For both 25(OH)D2 and 25(OH)D3, the linear range of quantitation is 0. 94-120 ng/mL, the limit of detection is 0 . 12 ng/mL ( S/N=3 ) , and the limit of quantitation is 0 . 94 ng/mL ( S/N=10 ) . The intra-day relative standard deviation ( RSD) values of 25(OH)D2 and 25(OH)D3 are 1. 4% -6. 6%, 3. 7% -7. 0%, respectively. The inter-day RSD values of 25(OH)D2 and 25(OH)D3 are 4. 0%-5. 3%, 3. 8-10. 6%, respectively. The recovery (mean±SD) in 5 consecutive of 25(OH)D2 is 98. 7%±4. 6%-108. 5%±6. 5%, and that of 25(OH)D3 is 94. 8%±6. 8%-101. 3%±2. 9%. DBS sample stability is confirmed by measuring identical DBS samples stored for 0 , 1 , 2 , 3 , 5 , 7 and 14 days at -20℃, 22℃, and 37℃, and an overall RSD°15% was observed under each temperature. DBS sample stability in freeze-thaw cycles is also confirmed by experimenting identical DBS samples up to 14 free-thaw cycles ( each cycle consisting of 23 h freezing at-80℃ followed by 1 h thaw at room temperature), and an overall RSD°15% is observed. The accuracy of 25(OH)D2 and 25(OH)D3 quantitation is validated by measuring a DBS sample prepared from NIST reference material SRM972 a Level 3 and the recovery is found to be 110 . 3% and 103 . 0%.

Preparation and evaluation of dried blood spots control materials for steroids / 临床儿科杂志

Objective To investigate the preparation method of dry blood spots (DBS) control materials for steroids used for internal quality control by liquid chromatography tandem mass spectrometry (LC-MS/MS). Methods Whole blood was collected and the blood cells and plasma were separated. The blood cells were washed by saline. The activated charcoal was added to the plasma. Standard substance was added to make different concentrations (low, medium, and high) of DBS control materials for steroids. The precision, accuracy, stability, and differences among different blood spots were detected and analyzed by LC-MS/MS. Results The inter-day precision and accuracy of DBS control materials for steroids were 2.4%-7.0% and 102.0%-111.0%, respectively, and the intra-day precision and accuracy were 5.1%-9.8% and 99.0%-114.8% respectively. The DBS control materials for steroids were stored for 5 months, and there was no difference among the different months (P>0.05). The coefficients of variation among different blood spots were small, 3.3%-8.2%. Conclusions The DBS control materials for steroids has good precision, accuracy and stability. The difference among different blood spots is small and meet the requirements of indoor quality control products. They can be used for the internal quality control in steroids detection by LC-MS/MS.

Effects of physical and chemical factors in environment for dried blood spot preparation of neonatal screening assay / 临床检验杂志

Objective To investigate the effects of physical and chemical factors in the environment for dried blood sample (DBS) preparation of neonatal screening assay.Methods A total of 60 normal and 120 positive DBS were prepared under control and 10 different conditions.Another 30 normal and 80 positive DBS were prepared under control and 7 different concentration gradients of formaldehyde.The levels of phenylalanine (Phe),glucose-6-phosphate dehydrogenease (G6PD),thyroid stimulating hormone (TSH) and 17α-hydoxyprogesterone (17α-OHP) were tested by time-resolved fluorescence immunoassay or fluorescence assay.Statistical analysis was performed using SPSS 22.0 software.Results Compared with the control group,the results of Phe were not significantly different (P ＞ 0.05) when the samples were dried under the formaldehyde sensitive threshold (4.62 to 6.95 ppm for 18 hours).G6PD levels were significantly lowered when the samples were dried under all the conditions except for fast cold drying (2 to 8 ℃ overnight and formaldehyde condition,0.30 to 0.38 ppm for 4 hours or 0.21 to 0.24 ppm for 18 hours).TSH and 17α-OHP levels were lowered obviously when the samples were dried under the conditions of humidity,UV and formaldehyde condition (TSH:0.32 to 0.52 ppm for 4 hours,0.38 to 0.45 ppm for 18 hours,17α-OHP:4.37 to 4.62 ppm for 4 hours,0.38 to 0.45 ppm for 18 hours).The results of Phe,G6PD,TSH and 17α-OHP were not statistically different with the control group when the samples were dried under the fast cold drying and 2 to 8 ℃ overnight.Conclusion The physical and chemical factors in the environment of DBS preparation should be related to the accuracy of neonatal disease screening closely.The necessary control factors including formaldehyde,ethanol,glacial acetic acid,ultraviolet irradiation,heat,humidity and decoration pollution may exhibit significant effects on the preparation of DBS.Fast cold drying and overnight at 2 to 8 ℃ could be available for DBS preparation.

Newborn Screening for Lysosomal Storage Disorders in Belgium The Importance of Sex- and Age-Dependent Reference Ranges

Abstract Lysosomal storage disorders (LSDs) are a group of metabolic disorders with various clinical presentations, which complicate diagnosis. A pilot study was performed to test the appropriateness and effectiveness of the newborn screening method for Pompe disease, Fabry disease and mucopolysaccharidosis (MPS) I in dried blood spots using liquid chromatography-tandem mass spectrometry. Around 20 000 newborn samples were analyzed for 3 lysosomal enzyme activities: ?-glucosidase (deficient in Pompe disease), ?-galactosidase (deficient in Fabry disease) and ?-iduronidase (IDUA, deficient in MPS I). Data were used for statistical analysis and to establish sex- and age-dependent reference ranges. Statistically significant higher ?-glucosidase, ?-galactosidase, and IDUA enzyme activities were observed in female newborns compared to male newborns. Newborns with a higher gestational age have a statistically significant lower ?-glucosidase, ?-galactosidase, and IDUA enzyme activities compared to newborns with a lower gestational age. For the first time, the data of a large-scale LSD study were used to assess statistical differences in enzyme activity in the newborn population, and these data highlight the importance of using reference intervals for lysosomal enzyme activities in function of sex and gestational age.

Valores de referencia de β-glucosidasa y quitotriosidasa en gotas de sangre seca de lactantes venezolanos / Reference Values for β-glucosidase and chitotriosidase using dried blood spots in Venezuelan infants

La enfermedad de Gaucher es un trastorno de herencia autosómica recesiva y la enfermedad de depósito lisosomal más frecuente causada por deficiencia de la actividad enzimática de la β-Glucosidasa. Objetivo: establecer valores de referencia de actividad enzimática lisosomal de β-glucosidasa y quitotriosidasa en lactantes en población Venezolana. Método: Se realizó un estudio prospectivo y transversal en 98 lactantes sanos con edades comprendidas entre 1 mes y 24 meses, de ambos sexos (48 femeninos y 50 masculinos). La actividad enzimática de β-glucosidasa y quitotriosidasa fue determinada en gotas de sangre seca (siglas en inglés, DBS) siguiendo el protocolo propuesto por Chamoles y col. El análisis estadístico de los datos se realizó con el programa estadístico SPSS Statistics 17.0 para Windows. Resultados: El rango de actividad enzimática para la β-Glucosidasa obtenido en esta investigación fue 2,3 - 12 nmol/ml/h, con una media de 6,7 ± 2,5 y para la Quitotriosidasa 0 - 44,2 nmol/ml/h con una media de 18,4 ± 10,4 nmol/ml/h, utilizando discos de papel de filtro de 3mm de diámetro con sangre seca (aproximadamente 3,6 μl de sangre). Conclusión: Los valores de referencia de actividad enzimática lisosomal en DBS para β-glucosidasa y quitotriosidasa son establecidos por vez primera en lactantes sanos venezolanos; no obstante, estos resultados difieren con los reportados en estudios internacionales, recomendándose la determinación de valores de referencias autóctonos en diferentes grupos etarios.

Gaucher´s Disease is an autosomal recessive disorder and the most common lysosomal storage disease caused by deficiency of β-glucosidase enzyme activity. Objetive: to establish reference values for lysosomal enzyme activity of β-glucosidase and chitotriosidase in Venezuelan infants. Methods:A prospective cross-sectional study was conducted in 98 healthy infants with ages ranging from 1 month to 24 months (48 females and 50 males). Enzymatic activity of β-glucosidase and chitotriosidase were determined in dried blood spots (DBS) following the protocol by Chamoles et al. Statistical analysis of data was performed with software SPSS 17.0 for Windows Statistics. Results: The range of enzymatic activity for β-glucosidase was 2.3 to 12 nmol/ml/h, with an average of 6.7 ± 2.5. Chitotriosidase activity was from 0 to 44.2 nmol/ml/h with an average of 18.4 ± 10.4 using 3mm diameter discs of filter paper with dried blood (approximately 3.6 μl of blood). Conclusions: The reference values of lysosomal enzyme activity in DBS for β-Glucosidase and quitotriosidase were established for the first time in healthy Venezuelan infants; however, these results differ from those reported in international studies, for which reason autochthonous reference values should be determined in different age groups.

Application of capillary electrophoresis by dried filter blood paper for screening of α-thalassemia in neonates / 国际检验医学杂志

Objective To investigate the application of capillary electrophoresis by dried filter blood paper for screening of α-thalassemia in neonates .Methods The hemoglobin (Hb) of 46 718 cases of neonatal dried heel blood spots were analyzed by the capillary electrophoresis and the content of HbA ,HbF ,HbA2 and abnormal Hb were detected ,the phenotype cases which was screened positive were recalled for genetic analysis .Results A total of 2 598 cases of Bart hemoglobin (Hb Bart′s) positive were detected in 46 718 cases of neonatal heel blood dried blood spots .The screening positive rate was 5 .56% (2 598/46 718) .A total of 477 cases of α-thalassemia gene carriers were confirmed by genetic analysis in the 544 cases which were recalled .The coincidence rate of Hb Bart′s screening and genetic diagnosis was 87 .68% (477/544) .By analyzing the relationship between the clinical pheno-types and the content of Hb Bart′s ,we found the Hb Bart′s content gradually increased with the severity of clinical phenotype ,and the difference was statistically significant (P= 0 .000) .Conclusion There is a good consistency between the capillary electrophore-sis of dried filter blood paper and the genetic analysis .It could be determined α-thalassemia clinical type according to the Hb Bart′s content .

Development of a thalassemia gene diagnosis method for dried blood spots / 国际检验医学杂志

Objective To devolope a method for extracting DNA from dried blood spots (DBS)and optimizing the operating procedure,which could be applied to clinical gene diagnosis of thalassemia.And the cross contamination of DBS punching and the storage stability of DBS were studied.Methods A total of 1 50 blood specimens were collected,and DBS were prepared.Circles (3 mm in diameter)were punched in the DBS,and eluted with lysis buffer.The eluting method and operating procedure were opti-mized.Genomic DNA extracted from the elution solution by magnetic beads,and were performed thalassemia gene test.Finally jud-ging whether the results of DBS and whole blood were consistent.Two methods of thalassemia gene test were used in DBS and the compatibility of DBS processing method was verified.Judging whether there was cross contamination of DBS punching by the thalassemia gene test results of blank hole which were punched in the blank filter paper between thalassemia positive DBS.The DBS storage stability in thalassemia gene test was verified by detecting the DBS which were dry stored at room temperature for 6 and 9 months.Results 5 circles (3 mm in diameter)DBS were vibrating eluted at 55 ℃ for 1 hour,the DNA concentration extracted from the elution solution was 10-20 ng/μL,which was dissolved in 50 μL solution,and the DNA quality was good.The thalassemia gene test results of DBS and whole blood were the same,and the DBS results of two thalassemia gene test methods were the same too. The cross contamination of DBS punching was not detected in thalassemia gene test.The DBS which were dry stored at room tem-perature for 6 and 9 months could be stably performed thalassemia gene test.Conclusion DBS could be used to perform thalassemia gene test,which is accurate,convenient and stable.It is an ideal way for specimen referral of thalassemia gene test.

Method evaluation of plasmodium DNA template extraction from dried blood on filter paper / 国际检验医学杂志

Objective To evaluate the method of plasmodium DNA template extraction from dried blood on filter paper . Methods Collectedand tested 47 blood samples of suspected imported malaria patients ,the DNA was extracted and tested by using conventional procedures and PCR ,then count and analyze test results of matched design .Results The Kappa value was 0 .492 when compared filter paper dried blood spots with thick and thin blood smear test results ,and the Kappa value was 0 .686 when com‐pared with whole blood sample .Using the results of thick and thin blood smear and whole blood samples as the gold standard to e‐valuate the sensitivity and specificity of filter paper dried blood spot method respectively ,the sensitivity was 75 .0% ,71 .4% and specificity was 78 .9% ,100 .0% .Conclusion Collected blood samples using filter paper can′t get good results in PCR test ,still needs further research .

Prevalence of Vitamin A Deficiency in Pregnant and Lactating Women in the Republic of Congo.

Vitamin A status in a sample of pregnant and lactating women living in several representative regions of Congo was assessed and compared between August and September 2004. This survey was conducted using a randomized two-stage cluster-sampling method with stratification on 90 clusters, each consisting of at least 15 women. Vitamin A status was determined in a total of 1,054 individuals, using the impression cytology with transfer (ICT) test, the modified relative dose response test (MRDR test) on dried blood spots (DBS), and clinical examination to detect signs of xerophthalmia. The clinical criterion defining vitamin A deficiency was the presence of active xerophthalmia (Bitot’s spots [X1B]), active corneal disease), and/ or night blindness (XN stage). The prevalence of clinical signs of stage XN and X1B xerophthalmia in the Republic of Congo was found to be 16% and 19% respectively. The prevalence of clinical signs (X1B) was greater in the rural north than in urban areas, with a gradient running from urban (5%) to rural area (33%); 27% of all the ICT tests showed that the subjects were suffering from vitamin A deficiency. The deficiency rates were significantly higher (p<0.001) in urban surroundings (Brazzaville) than in the rural northern regions. The biochemical MRDR test showed the presence of vitamin A deficiency (≥0.06) in 26% of the mothers in Brazzaville compared to 6% in the town of Kouilou; 44% of the women had retinol levels of <10 μg/dL in the rural north whereas these percentages were significantly lower in the urban areas surveyed (chi-square=62.30, p<0.001). A significant correlation was found to exist (p<0.001) between the ICT test and the MRDR test on DBS. In the population as a whole, 30% of the mothers suffering from malarial attack had abnormally low MRDR levels (≥0.06) compared to no malaria. The results of the present study confirm that vitamin A deficiency is a serious public-health issue in pregnant and lactating mothers in the Republic of Congo.