Dichlorophenolindophenol Test Research Articles

Efficacy of Dichlorophenolindophenol (DCIP) as Screening Test for Hb E: Revisited.

Hb E-beta thalassemia is a major public health problem in West Bengal, India and is the predominant symptom producing thalassemia in this part of the country. To search for an easy, reliable and cost effective screening method for HbE that can be used at the community level where more sophisticated methods are not readily available. And the DCIP test was performed for the purpose. Blood samples of 425 asymptomatic family members from 80 diagnosed cases of HbE beta Thalassemia patients were tested for Hb, RBC indices, DCIP test, HPLC, and in discordant cases confirmed by DNA mutation analysis. The present study shows DCIP screening test to have a sensitivity, specificity, positive predictive value and negative predictive value of 96.39%, 97.43%, 96.39% and 97.43% respectively. It also shows a false positive rate and false negative rate in 2.56% and 4.6% cases respectively. The advantage with DCIP over HPLC is that it can be easily performed at the community level by a person with minimum technical skill, few samples (even a single sample) can be tested at time, at a low cost.

A "One-Stop" Screening Protocol for Haemoglobinopathy Traits and Iron Deficiency in Sri Lanka.

Introduction: The high frequencies of carriers of severe haemoglobinopathies and of iron deficiency in Southeast Asia require reliable and affordable tests to improve on current screening procedures.Objectives: We evaluate a “one stop” approach using the THALCON dichlorophenolindophenol (DCIP) and one-tube osmotic fragility (OF) tests and measurement of Zinc Protoporphyrin (ZPP) to detect and distinguish HbE and β-thalassaemia traits from iron deficiency. We compare findings with current screening practice in Sri Lanka that relies on the identification of low mean red cell volume and/or mean red cell hemoglobin for this purpose.Methods: Between November 2017 and May 2018, we undertook a cross-sectional survey of secondary school students in Gampaha district, Sri Lanka. The THALCON–DCIP and OF tests were compared to capillary electrophoresis (CE), used as a gold standard to detect haemoglobinopathies. ZPP was measured in whole blood. Plasma ferritin and C-reactive protein (CRP) were measured in students with a raised ZPP concentration.Results: We collected venous blood samples from 1,324/1,332 (99.4%) students. The median age of the students was 17 (IQR 16–18) years, all were Sinhalese and 814/1,324 (61.5%) were female. CE identified 3 students with HbE trait and 26 students with β-thalassaemia trait. The THALCON–DCIP test was positive only in the 3 students with HbE (sensitivity 100%, 95% CI 29.2–100.0; specificity 100%, 95% CI 99.7–100.0). The THALCON–OF test identified all 26 students with β-thalassaemia trait (sensitivity = 100%, 95% CI 86.8–100.0) and 287 students with a normal CE result (specificity = 77.9%; 95% CI 75.5–80.1). It was also positive in 2/3 (66.7%) students with HbE trait. Iron deficiency (ZPP > 70 μmol/mol heme) was present in 118/1,240 (9.5%) students with a normal hemoglobin genotype, all of whom had plasma ferritin <15 ng/ml and CRP <5 mg/L.Conclusion: This one–stop approach offers reliable and affordable population screening for both haemoglobinopathy traits and iron deficiency in resource-limited settings where these conditions are common and ensures that iron supplements are targeted only to those who require them. Further work is warranted to refine the OF test to reduce the number of false positive results.

Evaluation of the URIT-2900 Automated Hematology Analyzer for screening of thalassemia and hemoglobinopathies in Southeast Asian populations

Background The effectiveness of the URIT-2900 Hematology Analyzer for screening of hemoglobinopathies commonly found in Southeast Asian populations was examined. Methods Appropriate cut-off values of MCV and MCH for screening of α 0 and β thalassemias were derived from the receiver operator characteristic curve conducted initially on 279 subjects with various thalassemia genotypes. Validation was performed additionally in a cohort of another unrelated 313 subjects. Results The best cut off values of MCV and MCH were found to be 78 fL and 27 pg, respectively. Using these cut off values in combination with the dichlorophenolindophenol test in screening of α 0 thalassemia, β thalassemia and Hb E in a cohort study revealed 100% sensitivity, 79.6% specificity, 80.0% positive predictive value and 100% negative predictive value. Conclusion The combined blood cell counting using the URIT-2900 Automated Hematology Analyzer and dichlorophenolindophenol test is suitable for population screening of thalassemia and hemoglobinopathies in Southeast Asia.

Thalassemia and hemoglobinopathies in pregnant Lao women: carrier screening, prevalence and molecular basis

To provide relevant evidence base for implementation of a prevention and control program for thalassemia in the Lao People's Democratic Republic (Lao PDR), we have evaluated a simple screening protocol and examined the prevalence and the molecular basis of thalassemia in pregnant Lao women. The study was conducted on 307 pregnant women attending the Mother and Child Health Hospital, Vientiane. Initial screening was performed locally, applying a combined osmotic fragility (OF) and dichlorophenolindophenol (DCIP) test. Erythrocyte counts were recorded. The remaining blood specimens were transferred to Thailand for further hemoglobin (Hb) and DNA analyses. Subjects were divided into four groups according to the results of the screening tests. Among 307 participants examined, 154 (50.2%) had negative results on both tests (-/-), 58 (18.8%) were positive on the OF test but not the DCIP test (+/-), 22 (7.1%) were negative on the OF test but positive on the DCIP test (-/+), and 73 (23.7%) were positive on both tests (+/+). As many as 25 thalassemia genotypes including various complex syndromes were observed. Three clinically important forms of thalassemia including alpha(o)-, beta-thalassemia, and Hb E were identified in 39 (12.7%), 11 (3.6%), and 93 (30.2%) subjects, respectively. The performance characteristic of the initial screening for these three forms of thalassemia was determined. The sensitivity, specificity, positive, and negative predictive values were found to be 99.2%, 85.5%, 83.0% and 99.4%, respectively. Therefore, thalassemia and hemoglobinopathies are prevalent and heterogeneous among the Lao population. Implementation of a simple carrier screening in pregnancy is practicable in the Lao PDR.

A simplified screening strategy for thalassaemia and haemoglobin E in rural communities in south-east Asia.

To evaluate a simple screening strategy for thalassaemia and haemoglobin (Hb) E in a prevention and control programme for thalassaemia in rural communities with limited resources. Blood samples from 301 Thai-Khmer participants were screened for thalassaemia and Hb E using a combined modified one-tube osmotic fragility (OF) test and a modified dichlorophenolindophenol (DCIP) precipitation test. Results were evaluated with standard haematological analyses including erythrocyte indices, Hb typing and quantification and polymerase chain reaction (PCR) analysis of alpha-globin and beta-globin genes. Participants were divided into four groups according to the results of the combined tests. Altogether, 104 of 301 participants (34.6%) had negative results on both tests; 48 (15.9%) were positive on the OF test but not the DCIP test; 40 (13.3%) were negative on the OF test but positive on DCIP test; and 109 (36.2%) were positive on both tests. No carrier of clinically significant forms of thalassaemia (alpha(o)-thalassaemia, beta-thalassaemia) or Hb E was found among the group that had negative results for both tests. All participants with Hb E had positive DCIP tests. Carriers of alpha+-thalassaemia or Hb Constant Spring could generate either positive or negative OF test results but they all had negative DCIP tests. Using both tests as a preliminary screening for the three important groups of carriers gave a sensitivity of 100% and a specificity of 69.8%. The positive predictive value of the combined test was 77.2%. The negative predictive value was 100%. Further evaluation of the screening system by local staff at three community hospitals found a sensitivity of 98.1-100% and a specificity of 65.4-88.4% with positive predictive values of 75.0-86.9% and negative predictive values of 98.1-100%. A combined test using OF and DCIP could be used as an effective preliminary screening alternative to an electronic blood cell count for identifying carriers with alpha(o)-thalassaemia, beta-thalassaemia and Hb E. The strategy should prove useful for population screening in prevention and control programmes in rural communities in south-east Asia where laboratory facilities and economic resources are limited.

A Reducing Substance in Tumours

THE indications previously obtained1 that the high reducing capacity of tumours in our dichloro-phenolindophenol test is due principally to a substance other than vitamin C have now been confirmed. In determinations of vitamin C content, by the histological tooth protection method, groups of guinea pigs were given 5 gm. each per day of freshly excised Jensen rat sarcoma (kindly provided by Mrs. Barbara Holmes). The various control groups received 0, 1, 2, 3 and 4 c.c. of orange juice, and 5 c.c. of orange juice plus 5 gm. of sarcoma. The degrees of protection afforded were found to be 1–2 for the sarcoma, 0, 1–2, 2–3, 3, 3–4 respectively for the orange juice controls, and 3–4 for orange juice plus sarcoma (4 = complete protection). It follows that 5 gm. of the tumour is equivalent in vitamin C content to no more than about 1 c.c. of orange juice.