Comparable performance of conventional and liquid-based cytology in diagnosing anal intraepithelial neoplasia in HIV-infected and -uninfected Thai men who have sex with men.

BACKGROUND

Anal cytology has increasingly been used to screen for anal intraepithelial neoplasia (AIN) among men who have sex with men (MSM) at increased risk for anal cancer. Use of liquid-based cytology has been reported to reduce fecal and bacterial contamination and air-drying artifact compared with conventional cytology. Costs associated with liquid-based cytology, however, may limit its use in resource-limited settings.

METHODS

Anal swab samples were collected from MSM participants and used to prepare conventional and liquid-based cytology slides. Abnormal conventional cytology results triggered referral for high-resolution anoscopy and biopsy. Agreement between the 2 cytology techniques and the positive predictive value ratios of histology confirmed AIN were calculated.

RESULTS

Among 173 MSM, abnormal anal cytology was identified in 46.2% of conventional and 32.4% of liquid-based slides. The results agreed in 62.4% of cases with a κ value of 0.49 (P < 0.001). HIV-infected MSM had a 3.6-fold increased odds of having discordant anal cytology results (95% confidence interval: 1.6 to 7.8; P = 0.001) compared with HIV-uninfected MSM. Histological AIN 2 and 3 were identified in 20 MSM. The positive predictive value ratios and 95% confidence interval indicated no difference between the 2 techniques.

CONCLUSIONS

Conventional anal cytology may be a preferred option for resource-limited settings given comparable performances to liquid-based cytology for the detection of AIN, although the agreement between the 2 techniques was lower among HIV-infected MSM. Due to high prevalence of abnormal anal cytology and AIN, health systems should prepare adequate infrastructure for high-resolution anoscopy services and AIN treatment.