Date of Award

1-1-2001

Thesis Type

Masters

Document Type

Thesis

Divisions

Institute for Advanced Studies

Department

-

Institution

Universiti Malaya

Abstract

The Epstein-Barr virus (EBV) is closely associated with nasopharyngcal carcinoma (NPC). The role(s) of EBV in NPC remains unclear but antibodies to two EBV proteins namely the viral capsid antigen (VCA) and early antigen (EA), are clinically useful diagnostic markers of NPC. The NPC scenario in Malaysia has been based on studies done on West Malaysian patients but not much has been described for NPC in Sarawak, East Malaysia. In this study, 164 NPC sera from newly histologically confirmed NPC patients were collected from the Radiotherapy Unit of Kuching General Hospital, Sarawak prior to radiotherapy. One hundred and forty seven non-NPC controls that were sex, age and ethnic groups matched were also collected. Among the NPC samples, the male to female ratio was 3.4 :1 with mean age of 47.9 years. The ethnic group distribution among the 164 NPC cases was as follows: 69 cases of Ibans (42.1%), followed by Chinese (22.5%) and the Bidayuhs (14.6%). The Ibans are 29.6% of the population while the Chinese make up 27.4%. The high incidence of Iban NPC patients is of interest since the origin of the Ibans is distinct from the Chinese who are known to have the highest incidence of NPC. The immunofluorcscence assay (IFA}) for anti-EBV antibodies was used to titrate the serum IgA and IgG against VCA and EA The present study found highly significant differences in the titres of all 4 markers (lgA/VCA, lgG/VCA , lgA/EA and lgG/EA) between NPC patients and the non-NPC controls. The geometric mean titres (GMT) for NPC sera were 34.8 for (IgA/VCA), 412.4 (lgG/VCA), 14.9 (lgA/EA) and 76.0 (lgG/EA), compared to 2.3, 9.6, 2.0 and 3.1 in the non-NPC control sera. These anti-EBV titres were found independent of sex, ethnic groups and age. For each serological marker, the sensitivity and specificity of the test determined the cut-off titre for positivity. A positive titre was ≥10, ≥160, ≥5 and ≥40 for lgA/VCA, lgG/VCA, lgA/VCA and lgG/EA respectively. The GMT of the serological markers in NPC patients with elevated antibody levels was 55.6 for lgA/VCA, 576.5 for IgG/VCA, 29.0 for lgA/EA and 166.3 for lgG/EA. With a cut-off titre at ≥160, lgA/VCA was the most sensitive marker (89.0%) with a 98.0% specificity. For lgA/EA at a cut-off titre of ≥5, it was the most specific marker (I 00.0%) but the least sensitive (75.0%). The sensitivity and specificity of lgA/VCA was 83.6% and 97.3% at a cut-off titre at ≥10. IgG/EA had a sensitivity of76.8% and specificity of99.3% at a cut-off titre of ≥40. A significant correlation was found between lgG/VCA (the most sensitive at ≥160) and the titres of the other 3 anti-EBV markers, indicating that if a patient has lgA/VCA antibodies, the other anti-EBV antibodies are likely elevated. One hundred and twelve (68.3%) of the 164 NPC patients were positive for all 4 markers, while 14 patients (8.5%) had no antibodies to any of the 4 EBV antigens. Eighteen (11.0%) NPC patients were positive for 3 markers, which included lgA/VCA, 10 (6.0%) NPC patients were positive for 2 markers, which also included 5 positive lgA/VCA samples and 10 (6.0%) NPC patients were positive for only 1 marker of which 2 were lgA/VCA positive. Based on the comparative sensitivity and specificity of the 4 anti-EBV antigens test, a combined use of lgA/VCA (≥160) and lgA/VCA (≥10) would improve the sensitivity of EBV serology in the diagnosis of NPC 12 90.9%.

Initial

snms

Additional Information

Dissertation (M.A) -- Institute for Advanced Studies, Universiti Malaya, 2001.

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