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Counseling on cannabis use in pregnancy


Choosing a screening tool

Universal prenatal substance use screening is recommended by the American College of Obstetricians and Gynecologists and the Centers for Disease Control and Prevention, but we don’t have any specific recommendations on what this means. Who should be screening, and what should that screening look like? Should we use a biologic screen, a standardized screening tool, or simply ask patients whether they use illicit substances?

Screening tools seem advantageous in that they are low cost, noninvasive, potentially comprehensive, and not subject to false-positive results as biologic screens can be – but which tool or tools are best? There are several validated screening tools that can be used outside of pregnancy to determine an individual’s use of illicit substances and whether or not that use is problematic, but previous studies have not used biologic markers to validate substance use screeners in pregnancy. Nor have studies compared screeners in pregnancy.

In our prenatal population in Baltimore, we have not been getting the answers we want using various nonvalidated screening tools. Approximately 30% of patients are positive for cannabis by urine screen, but only half tell us about their use.

Through research in our two prenatal care practices (one serving mostly privately insured and the other serving primarily Medicaid-eligible patients), we assessed both the accuracy and the acceptability of three substance use screening tools that are brief and that have been validated (for the general population) by the World Health Organization for screening of multiple substances: the 4P’s Plus (Parents, Partner, Past, and Pregnancy), the National Institute on Drug Abuse Quick Screen–ASSIST (Modified Alcohol, Smoking and Substance Involvement Screening Test), and the SURP-P (Substance Use Risk Profile–Pregnancy) scale.

In one study, published in May 2019 in Obstetrics & Gynecology, we recruited 500 pregnant women and administered these three tests to each of them.5 We then compared results with those of urine and hair drug testing, and checked the test-retest reliability of each test by readministering them (albeit by telephone) a week later. Although hair testing is not an indicator of current substance use, we used it to validate the screening tools on less-recent use.

The tests with the highest sensitivity and negative predictive values – the qualities we most want for screening – were the SURP-P and the 4P’s Plus (sensitivity of 92.4% and 90.2%, respectively). Overall they were highly sensitive screening tools across all trimesters, races, and age groups, making them more ideal screening tests than the NIDA Quick Screen–ASSIST.

Of the two tests, the 4P’s Plus screening tool was the one preferred by staff from both practices. In a companion qualitative study, we conducted focus-group discussions with 40 practice staff who were responsible for administering or overseeing patient screening.6 The staff, who were unaware of the sensitivity findings, were asked what they thought about the acceptability to patients of each of the three tools and their usability in practice.

Most of the participating staff preferred the 4P’s Plus screening tool for several reasons: It is easy to understand, is brief and to the point, and it has nonjudgmental language and tone. The screener first asks the patient about her parents’ and her partner’s use of alcohol and drugs, and then asks the patient about her own use of alcohol and tobacco. Affirmative responses to these questions lead to additional questions.

The premise is that one’s genetics, history, and current exposures – as well as one’s own use of tobacco and alcohol – are significantly associated with the use of illicit substances. If the patient reports no parental history or partner usage, and has never drank or smoked before, it’s extremely unlikely that she is using other drugs. The progression of questions does indeed seem less judgmental than immediately asking: “Do you use drugs?”

For us, the insight from this staff perception study combined with the findings on accuracy mean that the 4P’s Plus may be the most useful and acceptable screening tool for routine use in prenatal care.

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