Many taking PrEP in San Francisco not having recommended HIV and STI screens

Laboratory monitoring does not meet guideline standards in up to a third of people prescribed pre-exposure prophylaxis (PrEP), investigators report in Open Forum Infectious Diseases. Almost a quarter of people were not tested for HIV before starting PrEP and follow-up tests were not ordered for a third of testing intervals.

The study population consisted of a diverse group of people prescribed PrEP in primary care settings in San Francisco.

“We observed suboptimal lab monitoring and STI [sexually transmitted infection] testing by providers,” comment the authors. “Providers did not order HIV testing before almost one-fourth of PrEP initiators and one-third of follow-up intervals, which could increase risk of HIV drug resistance and forward HIV transmission after unrecognized HIV infection.”



The process of viral multiplication or reproduction. Viruses cannot replicate without the machinery and metabolism of cells (human cells, in the case of HIV), which is why viruses infect cells.

person years

In a study “100 person years of follow-up” could mean that information was collected on 100 people for one year, or on 50 people for two years each, or on ten people over ten years. In practice, each person’s duration of follow-up is likely to be different.

drug resistance

A drug-resistant HIV strain is one which is less susceptible to the effects of one or more anti-HIV drugs because of an accumulation of HIV mutations in its genotype. Resistance can be the result of a poor adherence to treatment or of transmission of an already resistant virus.

The investigators were also concerned about disparities in testing, with older and African-American patients less likely to receive recommended screening tests compared to other groups.

Clinical studies and real-world experience have shown that PrEP is a highly effective method of HIV prevention. Laboratory monitoring is needed to maximise the safety and effectiveness of the treatment. Guidelines recommend that individuals should be screened for HIV before starting PrEP and then every three to four months when taking the drugs. Although the two-drug combination used in PrEP is effective at preventing infection with HIV, it is not potent enough to suppress ongoing HIV replication and drug-resistant virus might emerge if an individual is taking the PrEP regimen when infected with HIV. It is also recommended that individuals receiving PrEP should have regular sexual health screens.

Little is known about the laboratory monitoring of people prescribed PrEP in primary care settings.

Investigators from San Francisco designed a study to determine if individuals were being screened for HIV before starting PrEP and also if they had regular follow-up tests. The researchers also checked whether people were having laboratory tests every six months to screen for bacterial STIs. Further analysis was undertaken to determine if any demographic factors were associated with the frequency of laboratory monitoring.

The study population consisted of 405 people who were prescribed PrEP at 15 primary care providers in San Francisco between 2013 and 2017. Several of the providers used a panel management model of care – a population-based healthcare approach that proactively focuses on the health of the entire clinic population, rather than only during clinic visits.

Most of the participants (85%) were male at birth and the median age was 34 years. The cohort was racially/ethnically diverse. Approximately two-thirds of participants had sex between men recorded as the reason for prescribing PrEP.

A baseline HIV test was ordered in only 77% of individuals, with 81% receiving STI screening before starting PrEP.

Older patients were less likely to receive a baseline HIV test than younger individuals.

Just over two-thirds (68%) of follow-up HIV tests and 67% of bacterial screens were carried out as per guidelines.

Older people, males and individuals receiving a PrEP re-fill lasting 90 days or more, were all less likely to have recommended follow-up HIV tests than other groups. Older individuals and African Americans were less likely to have follow-up STI screen than other groups. Providers caring for two or more PrEP patients and those using a patient management panel system of care were more likely to order recommended follow-up tests.

Overall STI incidence was 24 per 100 person-years during PrEP, lower than the rate seen in some other studies.

Two patients seroconverted for HIV, both infections occurring during breaks from PrEP.

“Our data suggest the promise of panel management, which could address disparities in PrEP testing,” conclude the authors. “Future research into innovative population management strategies could help minimize PrEP’s potential risks and maximize its preventive impact.”


Spinelli MA et al. Provider adherence to pre-exposure prophylaxis monitoring quidelines in a large primary care network. Open Forum Infectious Diseases, DOI: 10.1093/ofid/ofy099, 2018.