Clinical Practice Guidelines Antenatal Care — Module II
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- Cervical cancer and screening in Australia
- Prevalence of abnormal cervical smear results in pregnancy
- Cervical screening in pregnancy
- Diagnostic test accuracy
- Benefits and harms of screening
- Management of cervical abnormalities
- Discussing cervical screening
- Practice summary: cervical abnormalities
9.12Cervical abnormalitiesCervical screening aims to identify women who may have a cervical abnormality and require further diagnostic testing. BackgroundCervical cancer is one of the most preventable and curable cancers. Cells in the cervix show changes or ‘abnormalities’ before any progression to cancer, which takes around 15 years. Most low-grade abnormalities regress without treatment. High-grade abnormalities may occur after persistent infection with human papilloma virus (HPV), which is a sexually transmitted infection that generally has no symptoms and resolves within 2 years. In a small number of women, persistent infection with a high-risk type of HPV may eventually lead to cervical cancer (AIHW 2012). HPV 16 and 18 are high-risk types that are detected in 70–80% of cases of cervical cancer in Australia (AIHW 2012). A program of vaccination against HPV types 16 and 18 (as well as types 6 and 11, which have a lower risk of causing cancer but are associated with 90% of genital warts) was introduced in Australia in 2007 (DoHA 2013). Cervical cancer and screening in AustraliaPrevalence of HPV infection: An Australian study (before the introduction of the vaccination program) found that prevalence of HPV types 16 and 18 was similar for Aboriginal (9.4% and 4.1%) and non-Indigenous women (10.5% and 3.8%) (Garland et al 2011). Prevalence of HPV infection is higher among women from developing countries, with regions of high prevalence including Africa (22.1%) and Central America and Mexico (20.4%) (de Sanjose et al 2007). In all world regions, HPV prevalence is highest among women younger than 35 years (de Sanjose et al 2007). Other risk factors for cervical cancer: The risk of progression of HPV-related abnormalities to cervical cancer is increased by immunodeficiency (such as that caused by HIV infection), higher number of pregnancies, tobacco smoking, co-infection with other sexually transmitted infections and long-term (> 5 years) use of oral contraceptives (WHO 2006). Cervical cancer incidence and mortality: Incidence of, and mortality from, cervical cancer in Australia have both halved since 1991, remaining at their historic lows of 9 new cases and 2 deaths per 100,000 women since 2002 (AIHW 2012). Incidence does not vary significantly with geographical region but mortality is higher in remote areas (AIHW 2012). In 2004–08, the incidence of cervical cancer was 2.8 times higher among Aboriginal and Torres Strait Islander women than among non-Indigenous women (AIHW & AACR 2012), with data from 2006–10 showing that mortality was 4.4 times higher (AIHW 2012). Women from developing countries have an increased incidence, with the highest incidence (>45 per 100,000 women) found in Central and South America, eastern Africa, South and South-East Asia, and Melanesia (WHO 2006). Uptake of cervical screening: In 2009–2010, 57% of women in the Australian screening population had Pap smears, with participation highest among women aged 40–54 years (AIHW 2012). While cervical screening among women aged 20–24 years is low and decreasing, Australia is one of the few countries that screen this age group (AIHW 2012). Participation in screening did not vary significantly by geographical region but was lower in areas of social disadvantage (AIHW 2012). Information on participation for Aboriginal and Torres Strait Islander women is not available, as Indigenous status of participants is not collected, although there is evidence that this population group is under-screened (Coory et al 2002; Binns & Condon 2006). Prevalence of abnormal cervical smear results in pregnancyThe prevalence of abnormal cervical smear results in pregnancy does not appear to differ from the age-matched non-pregnant population (Muller & Smith 2005) and is estimated to be 0.5–3% depending on the population being screened (Brown et al 2005; Muller & Smith 2005; McIntyre-Seltman & Lesnock 2008). Cervical screening in pregnancyCurrent recommendations in Australia are that a Pap smear be offered to every well pregnant woman, without symptoms of cervical cancer, who has not had cervical screening within the past 2 years (NCSP 2009; RANZCOG 2009). Table 8 5: National Cervical Screening Program recommendations
Source: AIHW 2012. Summary of the evidenceDiagnostic test accuracyCervical cytology has a high specificity (62–98%) for detecting abnormalities in non-pregnant women, with few false positives. However, the low sensitivity (40–86%) increases the risk of false negatives (IARC 2005). The strength of cervical screening comes from repeated testing at agreed intervals, which allows abnormalities to be detected over the long pre-invasive stage of cervical cancers (Dickinson 2002). While cervical cytology appears to be equally accurate in pregnant and non-pregnant women, factors associated with pregnancy can complicate sampling and analysis and may result in false positives (Hunter et al 2008). Type of testOne small study found that rates of endocervical cell recovery in pregnant women are not statistically different using conventional or liquid-based cytology (Kruger et al 2003). Several studies affirm improved efficacy and safety of using a cytobrush when taking samples from pregnant women (Bond 2009). Timing of screeningWhile no specific evidence was found regarding when in pregnancy Pap smears should be performed, narrative reviews recommend that a Pap smear be done during the initial antenatal visit (Swenson 2001; Muller & Smith 2005; Govindappagari et al 2011) and preferably before 24 weeks gestation (NCSP 2009). Benefits and harms of screeningBenefits of screening include detection of previously unrecognised cervical abnormalities (Nygard et al 2007; Flannelly 2010). A potential harm is that the greater risk of false-positive results during pregnancy may result in unnecessary intervention and increased maternal anxiety (Flannelly 2010). Consensus-based recommendation xviii Offer women cervical screening as specified by the National Cervical Screening Program. Management of cervical abnormalitiesThere are few studies detailing the progression of low-grade abnormalities to cancer during pregnancy, but this appears to be extremely rare (NHMRC 2005). The NHMRC recommends investigation of abnormalities during pregnancy as follows (NHMRC 2005): in general, women with a low-grade abnormality should have a repeat smear in 12 months; and women with high-grade abnormalities should be referred to a colposcopist experienced in assessing the pregnant cervix.
cervical screening during pregnancy is only necessary for women who have been sexually active for more than 1 or 2 years and have not had a Pap smear in the last 2 years; cervical screening should be performed before 24 weeks gestation; a Pap smear is safe during pregnancy, although some spotting or bleeding may occur; and while low-grade changes require no further assessment during pregnancy, further assessment may be needed if high-grade changes are identified.
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