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


METHODS
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.


RESULTS
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%.


CONCLUSIONS
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.
Department of Clinica Microscopy, Khon Kaen University, Khon Kaen, Thailand.
Goonnapa
G
Fucharoen
Kanokwan
K
Sanchaisuriya
Nattaya
N
Sae-ung
Samrit
S
Dangwibul
Supan
S
Fucharoen
D015086:2,6-Dichloroindophenol; D000293:Adolescent; D000328:Adult; D002648:Child; D002851:Chromatography, High Pressure Liquid; D005838:Genotype; D006446:Hemoglobin E / Q000032:analysis* / Q000235:genetics; D006801:Humans; D008403:Mass Screening / Q000379:methods*; D016133:Polymerase Chain Reaction; D015995:Prevalence; D011320:Primary Health Care / Q000379:methods*; D016730:Program Development; D011933:Reagent Kits, Diagnostic; D012423:Rural Health; D012680:Sensitivity and Specificity; D013785:Thailand / Q000453:epidemiology; D013789:Thalassemia / Q000175:diagnosis* / Q000235:genetics / Q000517:prevention & control
D011933:Reagent Kits, Diagnostic; D006446:Hemoglobin E; D015086:2,6-Dichloroindophenol