School of Health and Social Care Screening for alcohol use in pregnancy Lesley Smith PhD Principal Lecturer Quantitative Research Methods School of Health & Social Care Oxford Brookes University Booze & Bumps School of Health and Social Care Outline • Aim of screening for alcohol misuse • Why it is important • Alcohol screening tools • Availability • Accuracy • Screening pregnant women • Screening tools in pregnancy • Systematic review • Conclusions School of Health and Social Care Aim of screening • Identify people at risk of alcohol related harm • Offer advice which reduces risk of potential harm • Recommendation in the DOH alcohol harm reduction strategy School of Health and Social Care Why screening is important • Increasing prevalence of drinking more than recommended levels in UK • Drinking levels and patterns in pregnant women unclear BUT heavier prenatal drinking associated with heavier antenatal drinking • Whilst low to moderate consumption inconclusive effects on the fetus – heavy and/or binge drinking harmful to the mother • Pregnancy presents an opportunity to identify and advise women on their drinking School of Health and Social Care Why is screening important? • Brief interventions shown to be effective in reducing alcohol consumption • though evidence in pregnant women less convincing • Screening without an intervention has also been shown to reduce alcohol consumption • Identification and advice can have effects lasting during post-partum period and subsequent pregnancies School of Health and Social Care Screening for alcohol use disorders (AUDs) • No ‘gold standard’ method for determining alcohol consumption • Relies on self-report • Validity of biomarkers poor • Standard questions about quantity and frequency of alcohol consumption requires a trained interviewer to elicit accurate responses (in-depth interview) • Impractical in the context of clinical practice School of Health and Social Care Alcohol screening tools • • Questionnaires administered by trained personnel e.g. G.P or nurse > 15 found for use in primary care e.g. • • • • AUDIT, MAST, CAGE Short versions AUDIT-C, AUDIT-3, FAST Overall score assigned Cut-off score defines screening positive for an alcohol use disorder School of Health and Social Care AUDIT-C Q1: How often did you have a drink containing alcohol in the past year? Never (0); Monthly or less (1); 2 to 4 times a month (2); 2 to 3 times a week (3); 4 or more times a week (4) Q2: How many drinks did you have on a typical day when you were drinking in the past year? 1 or 2 (0); 3 or 4 (1); 5 or 6 (2); 7 to 9 (3); 10 or more (4) Q3: How often did you have six or more drinks on one occasion in the past year? Never (0); less than monthly (1); monthly (2); Weekly (3); daily or almost daily (4) Scored on a scale of 0 - 12 (0 = no alcohol use). A score of 4 or more in men and 3 or more in women considered positive for hazardous drinking and need for further evaluation School of Health and Social Care The perfect test The size of the population is 100 and the number of people with the problem is 30. The prevalence of the problem is therefore 30/100 = 30%. Loong, T.-W. BMJ 2003;327:716-719 School of Health and Social Care Results of a screening test on a hypothetical population Loong, T.-W. BMJ 2003;327:716-719 School of Health and Social Care Measures of accuracy • Sensitivity is the probability of a positive test in a person with an AUD (true positive) • Specificity is the probability of a negative result in a person with no AUD (true negative) • Predictive values (PPV & NPV), Likelihood ratios (LR), diagnostic odds ratios DOR) School of Health and Social Care Sensitivity of a test The test has correctly identified 24 out of the 30 people who have the disease. Therefore the sensitivity of this test is 24/30 = 80%. Loong, T.-W. BMJ 2003;327:716-719 School of Health and Social Care Specificity of a test The test has correctly identified 56 out of 70 well people. The specificity of this test is therefore 56/70 = 80%. Loong, T.-W. BMJ 2003;327:716-719 School of Health and Social Care Limitations of existing tools • Most existing alcohol-use screening tools developed for use in men • Developed to detect alcohol dependency • Different thresholds for harmful drinking in men and women School of Health and Social Care Screening for alcohol use in pregnant women • Lack of consensus for a definition of harmful drinking in pregnant women • In UK current recommendation is to elicit response to a single question at booking interview • Inconsistent screening by midwives • When is best time to screen and resources? School of Health and Social Care Screening for AUDs in pregnant women • Clinical guidelines for drinking levels • Clinical guidelines for monitoring drinking levels limited – SIGN, BMA report School of Health and Social Care Newer screening tools • T-ACE • Test score 2 or more positive for risk drinking • Risk drinking defined as 3 units or more of alcohol per day while pregnant • TWEAK • 5-item instrument • Risk drinking defined as at least 3 units a day or 14 drinks a week • Test score 2 or more positive for risk drinking School of Health and Social Care T-ACE • T Tolerance: How many drinks does it take to make you feel high? (> 2 drinks = tolerance) • A Have people Annoyed you by criticising your drinking? • C Have you ever felt you ought to Cut down on your drinking? • E Eye opener: Have you ever had a drink first thing in the morning to steady your nerves or get rid of a hangover? Sokol et al. 1989 School of Health and Social Care Systematic review - methods • Comprehensive searches of electronic current to June 2008 and reference lists of reviews and articles • Cross-sectional studies comparing an alcohol screening questionnaire with a structured interview (reference test) • Risk drinking, alcohol abuse or alcohol dependency School of Health and Social Care Results – study selection Titles and abstracts retrieved from electronic and bibliographic searches (n = 1,374) Articles excluded after screening title and abstract (n = 1,342) Potentially relevant articles retrieved for further consideration (n = 32) Articles meeting eligibility criteria for systematic review (n = 6) Excluded articles (n = 26): Not primary study (review, guidelines, editorial or letter (n = 10) Not a screening accuracy study (n = 7) Not risk drinking (1) Ineligible reference standard for detection of alcohol consumption (n = 4) Brief questionnaire not used as index test (n = 1) Population not exclusively antenatal (n = 1) Duplicate report of an included study (n = 1) Unavailable from British Library (n = 1) School of Health and Social Care Results – risk drinking Study Sokol 89 Russell 94 Russell 96 Chang 98 Prevalence 42/971 (4.3%) 270/4743 (5.7%) 181/2717 (6.7%) 114/350 (33%) Tool SENS SPEC PPV CAGE 0.38 0.92 0.18 T-ACE 0.69 0.89 0.23 CAGE 0.49 0.93 0.30 T-ACE 0.70 0.85 0.22 TWEAK 0.79 0.83 0.22 T-ACE 0.88 0.79 0.23 TWEAK 0.91 0.77 0.22 T-ACE 0.92 0.38 0.39 SMAST 0.11 0.96 0.55 Dawson 2005 45/256 (17.6%) AUDIT-C 0.95 0.85 0.57 Dawson 2001 34/404 (8.4%) TWEAK 0.71 0.73 0.19 Positive predictive value Positive predictive value refers to the chance that a positive test result will be correct. That is, it looks at all the positive test results. 24 out of 38 positive test results are correct. The positive predictive value of this test is therefore 24/38 = 63%. Loong, T.-W. BMJ 2003;327:716-719 School of Health and Social Care Conclusions • T-ACE, TWEAK and AUDIT-C most promising to detect risk drinking • AUDIT-C also promising to detect past-year alcohol use disorder or past-year dependence • CAGE and SMAST of low to moderate accuracy School of Health and Social Care What makes a good screening test? • Accurate • discriminate risk drinkers from low-risk drinkers • Demonstrable benefits over existing practice • Easy to deliver • time, context and environment • Acceptable to women and caregivers School of Health and Social Care Summary • Numerous screening tools available • Few tested in pregnant women • All US studies and largely low socioeconomic groups • Unclear which tool would be most accurate and acceptable to women and midwives in the UK • Methodological limitations indicate evaluation in a UK population is warranted before widespread use is recommended School of Health and Social Care