The number of HIV
transmissions can be reduced by tracing patients who drop out of HIV care,
according to a mathematical model published in the online edition of the Journal of Acquired Immune Deficiency
Syndromes. Investigators based the model on data obtained from 1000 people receiving antiretroviral therapy in Malawi. Rapidly re-engaging
patients with care services prevented approximately four new infections over five years.
It was necessary to trace around 120 patients to prevent one infection,
but the investigators think the effort would be worthwhile “since a newly
infected patient will need life-long treatment and care costing thousands of
dollars, and HIV infection can cut short a patient’s life.”
therapy that suppresses viral load to undetectable levels in associated with a
near-zero risk of HIV transmission. However, many patients drop out of regular
care and interrupt their treatment, thus allowing their viral load to rebound,
increasing the risk of passing on HIV to sexual partners, as well as the risk of damage to their own immune system and health.
team of investigators wanted to see if re-engaging patients who were 'lost to
follow-up' would help prevent new HIV infections.
developed a mathematical model based on the observed rate of loss to follow-up
and the cumulative viral load of 1000 patients receiving antiretroviral therapy
The model included
- No patients lost to follow-up.
- No tracing of patients lost to
- Immediate tracing of patients
who missed appointments.
- Delayed tracing (over six
months) of patients dropping out of care.
Overall, 440 people were lost to follow-up at some point over the five years of the study.
load varied according to retention in care and speed of return to follow-up if
care was interrupted.
remained in continuous care had a cumulative viral load of 3.7 million
copies/ml. This compared to 8.6 million copies/ml for patients who dropped out of
care and never returned, and 8.0 million copies/ml for patients who returned to care after six or
more months. Individuals who were immediately reconnected to care had a
cumulative viral load of 7.7 million copies/ml.
50% of patients returned to care within five years. This increased to 59% with
delayed tracing and 68% with immediate tracing.
There were an
estimated 33 new infections per 1000 patients over five years if patients
remained in continuous care. This increased to 54 onward transmissions per 1000
patients if no attempts were made to trace the patients who dropped out of
prevented 3.6 infections per 1000 patients, whereas delayed tracing prevented
2.5 onward transmissions per 1000 patients.
modelling study based on two ART programmes in Malawi found that tracing
patients [lost to follow-up] can slightly reduce transmission from patients who
started ART,” comment the authors. “The effect depends on the delay between
missed visit and tracing.”
If tracing was
immediate, an estimated 116 patients needed to be re-engaged with care to
prevent one new infection.
“If one tracing
clerk can trace 4-5 missing patients per day, preventing a single transmission
would require a 1.5 month workload,” calculate the investigators. “The…workload
is reasonable in light of the cost of each infection averted.”
conclude: “tracing patients [lost to follow-up] may efficiently reduce HIV
transmission in Malawi and similar settings”. However, they caution that transmissions
from patients who drop out of care cannot be prevented by tracing alone.
“Interventions to keep patients in care and monitoring of adherence and
treatment response accurately are likely to be of greater importance than
tracing patients lost to follow-up.”