Errors in Prenatal Diagnosis:
Mitigating Risk and Preventing harm
Professor Dilly OC Anumba
Chair in Obstetrics and Gynaecology, The University of Sheffield Medical School
Consultant in Obstetrics and Fetomaternal Medicine
Clinical Lead, Wesfield Fetomaternal Unit
Jessop Wing, Sheffield Teaching Hospitals
Sheffield UK
Outline
• Definitions
• Scope and classification of prenatal diagnostic
errors
• Epidemiology of errors
– Relative prevalence
– Contribution of system failures
– Contribution of individual and patient-related errors
• Strategies for preventing, investigating and
mitigating errors in prenatal diagnosis
What is a clinical error?
• Failure of a planned action to be completed
as intended, or the use of a wrong plan to
achieve an aim.
• Clinical intervention
– Appropriate but incomplete
– Erroneous
– Misdirected
– Mis-delivered
Classification of prenatal diagnostic
(PND) errors
• Individual errors
• Latent errors
– “errors waiting to happen”
– system failures: faulty systems, processes,
and conditions
Domains of PND errors
•
•
•
•
Diagnostic
Treatment
Preventive
Others- latent errors
Diagnostic
• Error/delay in diagnosis: fetal malformation
or disease
• Failure to employ indicated tests (e.g.
amniocentesis, chorionic villus sampling)
Diagnostic (2)
• Use of outmoded tests or therapy
– (e.g. inferior prenatal screening tests for aneuploidy
with poor sensitivities and high false positive values)
• Failure to act on results: of monitoring/testing
– Suggestion of fetal compromise and risk of in utero
demise
– Poor interpretation of antenatal surveillance CTG)
– Failure to act on +ve test, failure to stop acting on a
–ve test
Treatment
• Error in performance of
operation/procedure/test
– procedure-related fetal trauma
– miscarriage from invasive testing/therapy
– system failures in batch prenatal screening for
aneuploidy
– Computer errors
– technical errors in sample retrieval for genetic
investigations
Treatment (2)
• Error in administering treatment
– treating the “wrong” unaffected fetus in multiple
pregnancy
– Fetal trauma
• Error in dose or method of drug
• Delay in treatment/response to an abnormal
test
• Inappropriate (not indicated) care
Preventive
• Failure to provide prophylaxis
– maternal Rhesus sensitisation from failure to
administer prophylactic anti-D following
potential fetomaternal haemorrhage
• Inadequate monitoring or follow-up of
treatment
– Managing the small fetus on scan
Other system failures
• Failure of communication
• Equipment failure
– resuscitation equipment
– cytogenetic and molecular genetics
• Other system failure
SPECIFIC ERRORS
Specific errors
Prenatal
screening
Prenatal
diagnosis
Prenatal
treatment
interventions
Errors during prenatal screening
• Incidence data sparse eg universal Downs’
syndrome screening, offered all pregnant
women as standard antenatal care.
• Mistakes occur in relation to:
– Counselling: failure to offer recommended
testing
– Sampling
– Laboratory testing and quantification
Errors during prenatal screening
– Pregnancy dating
• Wrong dates, wrong risks for aneuploidy
– Wrongly filled Lab forms
– Wrong assessment of nuchal translucency by US
Errors may lead to false positive or negative
results
Would in turn affect parental uptake of
diagnostic testing
Typically, legal cases on antenatal screening can arise from failure to offer screening or failure, at
the fetal abnormality scan, to identify certain defects.
Fetal abnormality screening claims
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Errors during prenatal diagnosis
• Ultrasound errors
– 1st trimester errors – dating, anomalies
– 2nd trimester errors- the routine anomaly scan
– 3rd trimester errors - missed diagnosis not
followed up appropriately
– Special circumstances –multiple pregnancies
• Invasive testing errors - cytogenetic and
molecular genetics error
Detection rates for fetal abnormalities
UK anomaly detection rates
Bryant L, Fisher A, Vicente F. Social Research and Regeneration Unit A. Fetal Anomaly
Ultrasound Screening Programme Study: Literature Survey. Plymouth: University of Plymouth Centre; 2007.
Operator-dependent errors,
subject/patient dependent errors
• Insufficient skills/training/practice –
minimum prescriptions
• Maternal obesity
• Fetal position
• Oligohydramnios vs. renal agenesis
Maternal obesity and congenital malformations
Paldini Ultrasound Obstet Gynecol 2009; 33: 720–729
Technical factors contributing PND errors
Acoustic limiting factors
• Depth of insonation required
• Absorption of US energy (dropout)
by abdominal adipose
Tips for scanning obese women
Other remedies
• Fetal MR scans
• Amnioinfusion for oligohydramnios
Costs of errors in prenatal diagnosis
Pregnancy losses
Diminished
satisfaction,
patients and
professionals
Loss of trust in
health care
system
Disability
Survival with
morbidity
Additional care
necessitated by
errors
Lost income and
household
productivity
Consequences of prenatal diagnostic
errors
• Erroneous counselling,
• Wrong/inappropriate treatment options
• Wrong parental decisions
Serious Incident
• Definition: an incident that occurred in
relation to services and care resulting in one
of the following:
– Unexpected/avoidable death of one or more
patients, staff, visitors or members of public.
– Serious harm to patient(s), staff, visitors or
members of public or where outcome requires
life-saving intervention, major surgical/medical
intervention, permanent harm or will shorten life
expectancy or result in prolonged pain or
psychological harm.
Serious Incident (2)
• A scenario that prevents or threatens to
prevent a provider organisation’s ability to
continue to deliver healthcare services, for
example, actual or potential loss of
personal/organisational information, damage
to property, reputation or the environment,
or IT failure.
Serious Incident- screening
• Actual/possible failure at any stage in pathway
of screening service, which:
– exposes the programme to unknown levels of risk
that screening, assessment or treatment have been
inadequate
– and hence there are possible serious consequences
for the clinical management of patients.
• Level of risk to individual may be low, but
because of large numbers involved corporate
risk may be very high.
ERROR MITIGATION
Failsafe strategies during prenatal
screening
• Failsafe: back-up mechanism to ensure that if something
goes wrong in screening pathway, processes are in place to
(i) identify what is going wrong and (ii) what action follows
to ensure a safe outcome.
• Most screening risks/errors predictable and often arise
from systems failure than individual error.
• Failsafe aimed to “design out” or reduce errors
Implementation of Failsafe - roles
National:
• Assess screening pathway and identified areas of high
risk that require failsafe measures.
Regional:
• Team provide expert advice on reducing risks in local
programmes. Assess robustness of local arrangements
through audit, peer review and the investigation of
incidents.
Commissioners:
• Incorporate national guidance to reduce risk within
service specifications and oversee implementation and
functioning.
Providers:
• Review and risk assess local pathways against national
guidance and develop, implement and maintain risk
reduction measures.
Downs syndrome screening
Managing serious incidents in screening service
EXAMPLES OF ERRORS LEADING TO
LITIGATION
• Mrs. M, gave birth to a son GM. G suffers from Down's
Syndrome. It is a matter of admission that this was noted
immediately when he was born.
• In this action, the pursuers aver that members of the staff
of GRMH (for whom the defenders are vicariously liable)
negligently failed to diagnose Gary's condition, and
advise the pursuers of it, at the appropriate stage of
pregnancy. It is also averred that if the first pursuer had
been advised that the baby would be affected by Down's
Syndrome, she would have had the pregnancy
terminated.
• Damages are claimed, under various heads, in respect of
the loss, injury and damage suffered by the pursuers as a
result of this negligence. Negligence was admitted.
The standard of care: the tension between medical
opinion and parental autonomy
• A patient may say she understands although she
has not in fact done so ... It is common experience
that misunderstandings arise despite reasonable
steps to avoid them. Clinicians should take
reasonable and appropriate steps to satisfy
themselves that the patient has understood the
information which has been provided; but the
obligation does not extend to ensuring that the
patient has understood.
• Camb. Law J., 70 [2011], pp 523-547 at 538
Maurice and another v France (App no 11810/03)
[2005] ECHR 11810/03
• The applicants were man and wife. In 1990, the
applicants had their first child who was afflicted by
infantile spinal amyotrophy, a genetic disorder. In 1997,
the second applicant began her third pregnancy. She
requested a prenatal diagnosis, and was assured by the
hospital that the foetus was healthy and was not
suffering from infantile spinal amytrophy.
• The child was born, and within some two years it
became apparent that she did suffer from the condition.
• The applicants subsequently made a claim for
compensation for damage suffered as a result of the
child's disability. An interim award was made in the
applicants' favour.
System failures
(1) Millennium incident
• In calculation of prior risk the year of birth was recorded
as two digits
• After the millennium this resulted in women being
assigned negative ages i.e. approximately -80 to -60
years.
• Patient aged -80 similar to the probability of 14 year old
therefore risks calculated did not appear outrageous,
several months before decrease in screen positive rate
was identified
•
System failures
• Subsequent EU directive put Down’s Syndrome
screening software in a high risk category
(2) Missing data on request forms
• Lab has procedure of Faxing requests forms with
missing data to midwives for completion and return
• Some Faxes were not responded to and this was
not realised until it was too late for screening
• Labs need to have a robust system in place to chase
request forms with missing data
•
System failures
(3) Inadvertently altering parameters in Screening software
• Down’s risks were affected and were inaccurate for a period
and this led to retrospective recalculation
• There needs to be a robust procedure in place whenever
changes are made to any variable which is part of a
screening risk calculation algorithm including a change
control procedure to check risks on anonymised data sets
are the same or show the expected changes pre and post
change
Other incidents include:
• Misinterpretation of request form information e.g.
a gestation was written on a 2T form as
“15.3”. There was no scan information provided so
this was interpreted as a HC of 15.3 cm.
• Increase of Fb hCG if samples stored or transported
in warm conditions
• Incorrect risks due to donor date of birth not
included in IVF Down’s screen
Patients may not recover from a
serious error
Conclusion
• Errors do happen but effort should be geared
at peventing systemic errors
– Introduce failsafe strategies
– Service audit and evaluation of performance
– Infrastructural support
– Training and staff support
– Situational awareness
– Root cause analysis and interventions