A comparative study of two methods of large loop excision of the transformation zone.

Objective: To determine whether the conventional large loop excision of the transformation zone (CLLETZ) and the "top-hat" technique (THLLETZ) differ in (a) completeness of excision of the cervical lesion, (b) depth of cervical tissue excised and (c) adequacy of follow up by cytology and colposcopy.

Design: Retrospective case review.

Setting: University Teaching Hospital, London.

Sample: Five hundred and thirteen consecutive patients matched for age, parity, smoking history and referral cytology who had either CLLETZ (286-5%) or THLLETZ (227-44%) for cervical intraepithelial neoplasia (CIN).

Methods: All procedures were performed or supervised by BSCCP-accredited colposcopists. All cytology and histology were reviewed by two specialist cytohistopathologists. Cervical stenosis was defined as difficulty in or inability in obtaining an endocervical brush smear.

Main Outcome Measures: Depth of cervical tissue excised, histology of endocervical margins, post-LLETZ cytologic and colposcopic findings.

Results: The mean depth of excision in the CLLETZ group was 12.1 mm (SD = 4.4 mm) and 20.8 mm (SD = 6.4 mm) in the THLLETZ group. The incidence of involved endocervical margins was 2.8% in the CLLETZ group and 5.2% in the THLLETZ group (P= 0.1). There was CIN in the "top-hat specimen" of 10 THLLETZ cases (4.4%, CI = 95%). The first post-treatment cervical smear was inadequate in 5 (4.1%) cases in the CLLETZ group and 20 (11.7%) in the THLLETZ group (P= 0.022). Cervical stenosis was found in 21 (7.7%) cases in the CLLETZ group and in 64 (30.9%) cases in the THLLETZ group (P < 0.0001). Eleven (4%) patients in the CLLETZ group had cytological and/or colposcopic evidence of residual CIN compared with 12(5.8%) patients in THLLETZ group (P= 0.4). In the first follow-up assessment, 21.7% of the CLLETZ group had incomplete colposcopy compared with 48.7% in the THLLETZ group (P < 0.0001).

Conclusions: Compared with the CLLETZ, the THLLETZ (1) removed more cervical tissue but did not have a lower incidence of involved endocervical margins, and (2) resulted in significantly higher incidence of inadequate post-treatment colposcopic and cytological follow up. These data indicate that there is no justification to performing a "top-hat" LLETZ routinely.