Blind sampling is superior to anoscope guided sampling for screening for anal intraepithelial neoplasia

Abstract

Objectives: Anal cytology smears are either collected ''blind'' (swab inserted 4 cm into anal canal and rotated) or guided through an anoscope (transformation zone visualised and then sampled). We compared these smear techniques with respect to sample quality and patient acceptability. Methods: Using a paired, random sequence clinical trial, 151 homosexual men (n = 95 HIV positive) underwent both smear techniques at a single visit; smear order was randomised and specimens were read blind. Both techniques utilised a Dacron swab, with water lubrication. Cytological specimens were prepared using a liquid based collection method (ThinPrep). The outcome measures were cytological specimen adequacy, cytological classification, presence of rectal columnar, squamous and metaplastic cells, contamination, patient comfort and acceptability, and volume of fluid that remained after the ThinPrep procedure. Results: Regardless of smear order, guided smears were less likely to detect higher grade abnormalities than blind smears (15 v 27 cases, p = 0.001). Controlling for smear order, guided smears were more likely to be assessed as ''unsatisfactory'' for cytological assessment (OR 6.93, 95% CI 1.92 to 24.94), and contain fewer squamous (OR 0.20, 95% CI 0.04 to 0.94) and metaplastic cells (OR 0.12, 95% CI 0.03 to 0.54) than blind smears; there were no other statistically significant differences between techniques. Regardless of smear technique, first performed smears were more likely to detect a higher grade abnormality than second performed smears (23 v eight cases, p,0.001). Conclusions: Blind cytology smears are superior to anoscope guided smears for screening for anal neoplasia in homosexual men. It is established that homosexual men have high rates of anal cancer 1 and the presumed precursor lesion, anal intraepithelial neoplasia (AIN).2-5 These associations have led some to propose the screening of homosexual men by anal cytology smear, 6 7 although the harms and benefits of screening are not well understood.Past studies of AIN have used one of two techniques for the collection of anal cells, the ''blind'' method 2 3 8-16 and the anoscope guided method.4 15-21 Anoscope guided sampling allows directed sampling from the ano-rectal transformation zone, the area of the anal canal where squamous carcinoma and its precursors most frequently develop. 12However, ''blind'' or non-guided sampling is the most widely used technique, typically physician collected rather than self collected. 22There is an extensive literature describing comparisons between blind ''self sampling'' and speculum directed cervical smears, 23 but there has been little evaluation of physician collected anal smears. Unlike cervical smears, faecal contamination is an issue of concern with anal smears, with a resultant relatively high smear inadequacy rate. 16 24Furthermore, given the associations between anal human papillomavirus (HPV) infection and both anal cancer and AIN, 5 18 25 the sampling technique must provide adequate cellularity for both cytology and a...

Agreement between Methods for Diagnosing HPV-Induced Anal Lesions in Women with Cervical Neoplasia

“…In the present study, the material collected for anal cytology was unsatisfactory in 6.2% of smears, a similar percentage to that reported in a study using conventional medium [24] and in another using liquid medium [29]; however, it was higher than the percentages reported in a study on anal cytology in HIV-positive patients [23] and in another on genital neoplasia [30]. …”

“…Although the use of cytology for screening anal lesions is recent, sensitivity and specificity values are similar to those found for cervical cytology. A recent study showed that the technique of blind sampling for anal smears is better than anoscopy-directed sampling, which makes the method even simpler than cervical sampling [29]. Likewise, a cost-benefit analysis showed screening by anal cytology to be a viable option for use within the public healthcare service [41].…”

Description of a Pilot Anal Pap Smear Screening Program Among Individuals Attending a Veteran's Affairs HIV Clinic

“…Cervical brush and Dacron swabs have been shown to obtain good cellularity and high yield for AIN. 33,34 In our study, factors that could have been related to the elevated number of unsatisfactory results are lack of staff expertise in collecting anal Pap smears since the procedure was newly introduced in the clinic, and also the fact some patients may have had anal intercourse or anal manipulation within 24 h prior to the anal sample collection. Nonetheless, the results underscore the necessity of specialized training of clinicians in performing anal Pap smears and of routinely orienting the patients undergoing anal Pap smear screening to avoid anal intercourse, anal manipulation (with finger insertion or sexual aids), anal enemas or anal douche within 24 h prior to sample collection.…”

Rastreamento e seguimento dos portadores das lesões anais induzidas pelo papilomavírus humano como prevenção do carcinoma anal

“…15,19,20,[25][26][27][28] Temos empregado o colposcópio convencional e colhemos material do canal anal para esfregaço, antes de iniciar o exame. Avaliamos o períneo e a pele perianal dois a três minutos depois da aplicação de gaze embebida em ácido acético a 5%, e procuramos por áreas acetobrancas.…”