Table 1 Summary of study characteristics.

Forrest et al. (2008), Tasmania, Australia.

Controlled Before and After Study (CBA).

Patients with a genetic test result, showing that they carried a gene mutation.

Intervention sample

11 probands and 76 at-risk relatives (55% women) (average 7 relatives per participant).

Control sample

8 probands and 55 at-risk relatives (48% women) (average 7 relatives per participant).

Genetic conditions

Balanced reciprocal chromosomal translocation, hereditary breast and ovarian cancer (BRCA1/2), hereditary nonpolyposis colorectal cancer [Lynch syndrome], multiple endocrine neoplasia type 1, Peutz-Jegher syndrome, or an X-linked condition with re-productive implications.

Telephone follow-up at 2-4 weeks and 3-6 months to support communication to relatives.

Two years

Retrospective audit of files.

Proportion of at-risk relatives who had made contact with the clinical genetics service within 2 years of the diagnosis in the proband.

The difference in the frequency that at-risk relatives were “definitely informed” between the intervention and control cohorts was statistically significant (χ­² 6.52, P 0.01).

Powered to identify differences

Authors did not report a power calculation and due to small sample size, it is assumed the study was not sufficiently powered.

Kardashian et al. (2012), California, USA

RCT Pilot.

Women who received genetic counselling and tested positive for a germline BRCA1/2 mutation.

Genetic conditions in sample

BRCA1/2

An educational tool in the form of a binder given to patients to take away

Between two and ten months after results disclosure.

Usual care

Knowledge.

Participants’ report of sharing BRCA results with eligible family members and 2) participants’ report of relatives receiving BRCA testing.

Intervention

First-Degree Relatives 90% (p 1.00)

Second-Degree Relatives 75% (p 0.32)

Cousins 63% (p 0.86)

Control

First-Degree Relatives 88%

Second-Degree Relatives 38%

Cousins 40%

Power to identify differences

The study was not sufficiently powered to detect differences between groups.

Montgomery et al. (2013), Philadelphia, USA.

RCT.

Women aged 18 years and older, who completed genetic testing for BRCA1/BRCA2, and who had one or more living adult FDRs with whom she would share results.

Intervention

187 probands (100% women)

Control

158 probands (100% women)

1385 relatives in total (51% women) (average of 4 relatives per participant)

Genetic conditions in sample

BRCA1/2

A six-step communication strategy delivered in the pre and post results counselling sessions with a resource guide given to each patient.

Three months after results disclosure.

Wellness session

Self-reported informing relatives.

99% of probands shared their genetic test results with at least one relative, and 53% shared test results with all of their FDRs. There was no significant difference between the intervention and control group in the percentage of probands sharing test results, or in their difficulty and distress in sharing test results.

Power to identify differences

The study was sufficiently powered to detect differences, with a sample of 110 needed for each condition, which was achieved.

Hodgson et al. (2016), Victoria, Australia.

RCT

Patients first in family to be diagnosed, or have a child diagnosed, with a genetic condition or as a carrier of a genetic condition that has implications for others.

Intervention

45 probands and 554 at-risk relatives (87% women) (average of 12 relatives per participant)

Control

50 probands and 536 at-risk relatives (88% women) (average of 11 relatives per participant)

Genetic conditions in sample: BRCA1, BRCA2 and Lynch Syndrome, inherited cardiac conditions. A carrier for chromosomal anomalies i.e., translocations, X-linked conditions such as Fragile X syndrome and Duchenne/Becker muscular dystrophy.

Telephone follow-up at 3, 6, and 12 months based on the reciprocal engagement model.

18 months

Usual care

Proportion of at-risk relatives who contacted genetics services for information and/or genetic testing.

The adjusted OR, considering the clustering effect within families, was 1.30; and the 95% CI was 0.70–2.42, P = 0.40, so no significant difference was found between the intervention and control conditions.

Power to identify differences

The study was sufficiently powered, needing a sample of 151 relatives, which they achieved.

Eijzenga et al. (2018), Netherlands

RCT

Patients with a conclusive (pathogenic mutation) and inconclusive (yet an increased risk based on family history) DNA test result.

Intervention

148 probands (75% women)

636 at risk relatives (no gender information reported) (average of 4.3 relatives per participant)

Control

157 probands (75% women)

628 at risk relatives (no gender information reported) (average of 4 relatives per participant).

Genetic conditions in sample

Hereditary and familial cancer: Breast/ovarian and colorectal.

One off telephone counselling session based on motivational interviewing.

Four months

Usual care

Knowledge, motivation, self-efficacy, and self-reported informing relatives.

No differences were found between the groups for knowledge of whom to inform or information to convey, for motivation, or self-efficacy. No differences were found between the intervention and control group for correctly informed relatives. Intervention = 1st degree 94 (n) 82%, 2nd 84 (n) 75%. Control = 1st degree 91 (n) 83%, 2nd 81 (n) 78%. 60% reported over informing (informing relatives that were not at increased risk).

Power to identify differences

As there was limited information regarding the outcomes, the authors based their power calculations on expected differences between groups. 132 participants were required per group, which they did achieve, therefore the study was sufficiently powered.