Prevalence of antibody to human T cell leukaemia/lymphoma virus in women attending antenatal clinic in southeast London: retrospective study

Infection with human T cell leukaemia/lymphoma virus (HTLV) type I occurs mainly in Japan, central and west Africa, and the Caribbean basin. Infection confers a lifetime risk of 2-4% for adult T cell leukaemia or lymphoma and 0.2-5% for tropical spastic paraparesis. However, the incubation period for these conditions after naturally acquired infection may be several decades.¹ The virus is transmitted via infected lymphocytes, and in areas of high prevalence breast feeding is an important route of transmission, particularly if continued for over six months.²

We determined the prevalence of HTLV antibody in women who had attended antenatal clinics at King's Healthcare NHS Trust, southeast London, to assess whether antenatal screening should be considered locally.

Subjects, methods, and results

With the approval of the local ethics committee, we tested sera that had been collected routinely at antenatal clinics between January 1994 and December 1996 for HTLV antibody. The samples were anonymised for patient's name and hospital number, but data on ethnicity, age, and partner's ethnicity were retained.

We initially pooled sera from five separate samples in a single assay well and used an enzyme linked immunoassay for HTLV antibody (Murex Biotech, Dartford, product code GE80/81). When the assay was reactive for a pool, we tested each sample using the same assay. Reactivity was then confirmed with a passive particle agglutination test (Serodia HTLV-I, Fujirebio, Tokyo, Japan), and we used an immunoblot assay to discriminate between HTLV types (Inno-Lia, HTLV I/II antibody assay, Innogenetics NV, Belgium).

We tested 8656 samples altogether and identified 110 reactive pools. These pools yielded 34 samples positive for HTLV antibody (0.39%, 95% confidence interval 0.26% to 0.52%)—32 with HTLV type I (0.37%), one with HTLV type II (0.01%), and one that was untypable. One sample gave an indeterminate antibody result. The table shows the overall results.

Comment

We found the seroprevalence of antibody to human T cell leukaemia/lymphoma virus was 0.39% among pregnant women in southeast London over a 36 month period. This result probably reflects the ethnic composition of the local residents of Lambeth, Lewisham, and Southwark, about 18% of whom are black (1991 census data).

The policy of not screening for HTLV antibody in pregnant women and in blood and organ donors is partly based on its perceived low prevalence and the low lifetime risk of associated disease. Although the cost of antenatal screening could be limited by selecting those women thought to be at high risk, this would require knowledge of the ethnicity details of current and previous sexual partners in order to be comprehensive. Such information might be difficult to obtain. In our study HTLV infection was not limited to women who described themselves as black African or black Caribbean, a finding that was also reported in the West Midlands.³ Three white women were infected, of whom two were born in Britain and one in Jamaica, and all three had black Caribbean partners. We also found HTLV antibody in 10 women born in Britain who described themselves as either black African of black Caribbean.

The prevalence of HTLV antibody was similar to that reported for HIV in the same population at the same time.⁴ With appropriate counselling, screening for HTLV should be accepted in the same light as testing for HIV, which has recently been recommended as part of the routine antenatal screening programme.⁵ However, unlike HIV infection, infection with HTLV is less likely to become clinically apparent, and the factors conferring a high risk of developing associ- ated disease have not been defined. In the mean- time, antenatal screening could help limit vertical transmission.

Table 1.

Results of testing sera from women attending antenatal clinics for antibody to human T cell leukaemia/lymphoma virus (HTLV)

Ethnic group	1994			1995			1996			Total
	No of patients	No (%) of positive results		No of patients	No (%) of positive results		No of patients	No (%) of positive results		No (%) of patients	No (%, 95% CI) of positive results
Black African	512	7* (1.37)		567	2 (0.35)		624	3 (0.48)		1703 (19.67)	12 (0.70, 0.3 to 1.1)
Black Caribbean	402	6 (1.49)		403	10 (2.48)		457	3 (0.66)		1262 (14.58)	19 (1.51, 0.8 to 2.2)
Black other†				18	0		36	0		54 (0.62)	0
White	1043	3 (0.29)		1045	0		1155	0		3243 (37.47)	3 (0.09, 0.0 to 0.2)
Mixed race	87	0		87	0		103	0		277 (3.20)	0
Indian, Pakistani, Bangladeshi	79	0		71	0		91	0		241 (2.78)	0
Asian, oriental	43	0		51	0		70	0		164 (1.89)	0
Others	88	0		137	0		166	0		391 (4.52)	0
Not stated	745	0		330	0		246	0		1321 (15.26)	0
Total	2999	16 (0.53)		2709	12 (0.44)		2948	6 (0.20)		8656	34 (0.39, 0.26 to 0.52)

^*Includes one infection with HTLV type II and one untypable infection. All other positive results were for HTLV type I. 

^†Not included as an option in ethnic group until 1995.