Diagnostics & Counselling: Variant Reporting & Counselling Models

Short version. Once a family-history pattern raises a hypothesis, the diagnostic pathway runs through test choice, variant classification (the ACMG/AMP framework of Richards et al. 2015, Genet Med 17:405), secondary-findings management (the ACMG SF list, currently v3.3 — Miller et al. 2025, Genet Med 27:101391, adding ABCD1, CYP27A1, and PLN), and a result-disclosure conversation framed by one of several counselling models. The early non-directive tradition, articulated by Reed and his successors, gave way over the last two decades to a richer literature on the counselling relationship; the Reciprocal-Engagement Model of Veach, Bartels & LeRoy 2007 is the most cited contemporary articulation. Cascade testing for at-risk relatives, the duty-to-warn debate (ASHG 1998 statement, Am J Hum Genet 62:474), and reproductive-options education complete the survey.

Molecular-genetic test ordering pathways

Test selection follows the question. The standard taxonomy taught in clinical-genetics curricula:

Single-gene Sanger sequencing: testing for a known familial variant in an at-risk relative; confirming a variant identified by a panel or exome. Cheap, fast, definitive for the targeted variant.
Multi-gene panel: simultaneous sequencing of a curated set of genes for a phenotype (hereditary breast and ovarian cancer; arrhythmogenic cardiomyopathy; epilepsy). The current default first test for many phenotypes; balances breadth against the burden of variants of uncertain significance (VUS).
Clinical exome sequencing (CES): sequencing of all protein-coding regions, with analysis restricted to a phenotype-driven gene list. Used where the phenotype is broad or syndromic and the targeted panel has not yielded a diagnosis.
Clinical genome sequencing (CGS): sequencing of the whole genome, including non-coding regions, structural variants, and mitochondrial DNA. Increasingly used in rare-disease diagnostics and now the standard offering of programmes such as the NHS Genomic Medicine Service in the UK.
Chromosomal microarray (CMA): detection of copy-number variants down to the level of small (~50 kb) deletions and duplications. The first-tier test in unexplained intellectual disability, congenital anomalies, and autism spectrum disorder presentations, established by Miller et al. 2010 (Am J Hum Genet 86:749).
Karyotype with FISH: classical cytogenetic analysis. Still used where a balanced rearrangement is suspected, in haematology, in prenatal cytogenetics, and to characterise marker chromosomes. Notation follows ISCN.
Methylation studies, MLPA, repeat-expansion testing, mitochondrial sequencing: targeted assays for specific phenotype categories.
Long-read sequencing: now entering routine practice for short-tandem-repeat disorders and structurally complex regions.

Test ordering pathways in the UK NHS are codified in the National Genomic Test Directory; in the US they sit within the test-menus of CAP/CLIA-accredited laboratories and within the ACMG points-to-consider statements. Either way, the trainee learns to match the question to the assay rather than to default to the broadest available test.

Pre-test counselling and informed consent

Pre-test counselling in genetics is a structured conversation that covers: the nature of the condition; the purpose and limits of the proposed test; the possible result categories (pathogenic, likely pathogenic, VUS, likely benign, benign — see below); the implications of each category for the proband and for relatives; the option of not testing; the secondary-findings policy of the laboratory; the practical aspects (cost, turnaround, sample); the consent decision; and the result-disclosure plan.

Informed consent in a genetics context has unusual features compared with other medical consent: results may have implications for biological relatives who have not consented; results may have implications for insurance and employment in jurisdictions where statutory protection is partial; results from research-grade testing carry different weight from results from accredited diagnostic testing; and the meaning of a result may change over time as the literature on a variant evolves. The ESHG and ACMG have each issued points-to-consider documents on consent for sequencing-based testing; both emphasise the need to discuss the secondary-findings policy explicitly before the test is run.

The ACMG/AMP variant-classification framework

The standard variant-classification framework is the joint ACMG / Association for Molecular Pathology guideline Richards et al. 2015 (Genet Med 17:405). The framework defines five tiers and a structured set of evidence criteria:

Pathogenic (P): very strong evidence of pathogenicity (well-established functional studies; same amino-acid change as a previously established pathogenic variant; etc.) plus supporting evidence.
Likely pathogenic (LP): combinations of strong / moderate / supporting evidence summing to likely pathogenic by the criteria.
Variant of uncertain significance (VUS): insufficient evidence either way, or conflicting evidence.
Likely benign (LB): criteria pointing toward benignity but not meeting the threshold for benign.
Benign (B): very strong evidence of benignity (very common in population databases, direct functional or segregation evidence).

The 2015 framework defines the codes for each piece of evidence (PVS1 for null variant in a gene where loss of function is a known mechanism; PS1 for same amino-acid change as established pathogenic; PM2 for absence from population databases; etc.) and the combination rules for arriving at a tier. Subsequent specifications — the ClinGen Variant Curation Expert Panel guidance on individual genes, the SVI Working Group revisions on individual criteria (e.g. PVS1 reframed by Abou Tayoun et al. 2018; PS3 / BS3 reframed by Brnich et al. 2019) — are layered on top.

The framework is taught alongside the principal data resources used to apply it: ClinVar for prior submissions and consensus, gnomAD for population allele frequencies, HGMD for the historical literature, and per-gene specialist databases (LOVD, BRCA Exchange, etc.). Variant-curation training is increasingly delivered through structured exercises — the trainee classifies a variant from raw evidence and compares to a panel-curated answer.

Secondary and incidental findings

When sequencing is broad, results unrelated to the indication may emerge. The ACMG Secondary Findings (SF) list, established in Green et al. 2013 and refined through the v2.0 update (Kalia et al. 2017, Genet Med 19:249), specifies a set of genes for which the laboratory is recommended to look at and report on regardless of the primary indication, on the grounds that the conditions are medically actionable and the burden-versus-benefit calculation falls on the side of return. The list has been updated periodically; the current version is ACMG SF v3.3 (Miller et al. 2025, Genet Med 27:101391; published February 2025), succeeding ACMG SF v3.2 (Miller et al. 2023, Genet Med 25:100866). The 2025 update adds three genes: ABCD1 (X-linked adrenoleukodystrophy, OMIM 300100), CYP27A1 (cerebrotendinous xanthomatosis, OMIM 213700), and PLN (dilated cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy, OMIM 609909). The list evolves; readers should always check acmg.net for the current version.

The SF list applies in the context of clinical sequencing; research sequencing has its own framework. The patient may opt out of SF reporting at the consent step in most centres, an opt-out that has been the subject of substantial bioethics literature on the right not to know. ESHG guidance has tended toward a more conservative position than ACMG — offering rather than recommending return — reflecting a difference in regulatory and cultural context.

The result-delivery session

The result-delivery (or "disclosure") session is a structured conversation, separate from the pre-test session, in which the result is communicated. The literature on result delivery in genetics is extensive; the conventions taught in most curricula:

Results are delivered in person where the result is significant and the patient is local; remote delivery (telephone, video) is increasingly common and the literature on remote disclosure has grown rapidly during and since the 2020 COVID-19 period.
The patient is asked at the start what they understand of their referral and what they are expecting; this lets the clinician calibrate the explanation.
The clinician states the result clearly and early; "headline first" is the standard guidance. The implications and the discussion follow.
Time is allowed for emotional response; the conversation does not move on to next steps until the patient has had space to react.
Written documentation (the result letter, the variant report) is provided in addition to the verbal account.
Cascade-testing options for relatives are introduced as a question rather than as an instruction; the patient's wishes about communication with relatives are explored.
Follow-up is offered.

Carrier status and the carrier-result conversation

Carrier status — one pathogenic variant in a gene associated with an autosomal recessive or X-linked condition — is reported in the same framework but communicated differently. The carrier conversation is reproductive in framing: the implication is for offspring with a partner who is also a carrier, not for the carrier's own health. The conversation typically covers carrier-screening of the partner, the residual risk of an undetected variant in the partner, the reproductive options if both partners carry, and the cascade-testing question for the carrier's siblings (each first-degree relative has a 50% prior probability of being a carrier).

Counselling models: from non-directive tradition to Reciprocal-Engagement

The early genetic-counselling literature, descending from Sheldon Reed's 1947 framing, emphasised the non-directive stance: the counsellor presents information, the family makes the decision. The position was both ethical (the family's reproductive and testing decisions are theirs) and pragmatic (the counsellor cannot fully reckon with the family's values and circumstances). Non-directiveness was the field's defining stance for several decades.

Two evolutions in the contemporary literature:

Shared decision-making as a clinical-medicine framework imported into the counselling encounter: the counsellor and patient co-deliberate, with the counsellor's clinical and value-aware judgement on the table rather than withheld.
The Reciprocal-Engagement Model (Veach, Bartels & LeRoy 2007, J Genet Couns 16:713): a structured account of the counselling relationship across five tenets — genetic information is key; relationship is integral to genetic counselling; patient autonomy must be supported; patients are resilient; patient emotions make a difference. The model is now the most cited contemporary articulation in the curriculum literature.

The contemporary framing of the contemporary practice is the Resta 2006 definition: "Genetic counseling is the process of helping people understand and adapt to the medical, psychological and familial implications of genetic contributions to disease." The language of adapt rather than decide is deliberate: it foregrounds the family's process over the clinician's information transfer.

Psychosocial assessment

Counselling curricula treat psychosocial assessment as a core competency. The trainee learns to assess: the patient's emotional state at presentation; the patient's family situation, support systems, and likely audience for the result; pre-existing psychiatric conditions and their possible interaction with the result; coping styles (information-seeking versus information-avoiding); and the support resources available. Standardised tools (the genetic-counselling-specific psychosocial assessment instruments developed in the literature) are used in some centres; structured interview is universal.

Cascade testing for at-risk relatives

Cascade testing — offering at-risk relatives the option of being tested for a known familial variant — is the clinical-public-health strategy that converts a diagnosed proband into preventive opportunities for relatives. The literature on cascade testing covers the ethical question (whose responsibility to communicate to whom), the practical questions (the proband-mediated letter; direct-contact pilots in some jurisdictions), and the systems questions (cascade-testing rates remain consistently lower than the public-health model would predict; Sturm et al. 2018 and similar studies document this gap).

Where cascade testing is supported by family-history modelling, Evagene's calculator pages for hereditary conditions provide teaching implementations of the published algorithms: BRCAPRO, MMRpro, PancPRO, the Lynch syndrome family-history calculator, and hereditary cancer risk assessment. For BOADICEA, Evagene exports a ##CanRisk 2.0 file for upload at canrisk.org; clinical-grade BOADICEA computation is run there off-platform. The Tyrer-Cuzick implementation in Evagene is an IBIS-style approximation of the published Tyrer / Duffy / Cuzick 2004 algorithm, not the official IBIS Breast Cancer Risk Evaluator binary; see Tyrer-Cuzick alternative.

The duty-to-warn debate

Whether and how a clinician's duty to a proband extends to the proband's at-risk biological relatives is one of the most-discussed ethical questions in genetics. The American Society of Human Genetics 1998 statement (Am J Hum Genet 62:474) set out a structured position: the clinician's primary duty is to the proband, communication with relatives normally proceeds via the proband, but in narrow circumstances (a serious and foreseeable harm; a high probability the relative will benefit from knowing; the proband has been given reasonable opportunity and refused) the clinician may be justified in communicating directly. The 1998 statement remains widely cited as the structured starting point. The ELSI page covers subsequent developments including the UK ABC v St George's Healthcare NHS Trust litigation; see ethics, legal, and social issues.

Reproductive-options education

Reproductive-options education is a teaching topic in its own right, conducted with deliberate neutrality. The options described in the literature (the framing here is descriptive, not advisory):

Natural conception with prenatal diagnosis (PND): chorionic villus sampling at ~11–13 weeks; amniocentesis at ~15–20 weeks; non-invasive prenatal testing (NIPT) for screening of selected aneuploidies and, increasingly, single-gene conditions.
Preimplantation genetic testing (PGT): PGT for monogenic disease (PGT-M) where a familial variant is known; PGT for chromosomal structural rearrangement (PGT-SR); PGT for aneuploidy (PGT-A) in IVF more broadly. Carried out in conjunction with in-vitro fertilisation.
Donor gametes from a non-carrier donor.
Adoption.
Choosing not to have biological children.
Choosing to proceed without testing.

Counselling around these options is non-directive in the traditional sense: the counsellor presents information, the family decides. Polygenic embryo selection — an emerging and contested area — is covered on the ELSI page.

Boundary statement

This page describes molecular diagnostics and counselling as discussed in the published literature. It is a teaching survey, not a clinical protocol. Variant classification, secondary-findings management, and the result-disclosure conversation as practised in any particular case are decisions for the responsible clinician, working within the framework of the laboratory, the patient, and the institution. Evagene's calculators are illustrative implementations of published algorithms intended for research and teaching; clinical-grade computation, where available, is provided off-platform (BOADICEA at canrisk.org; the official IBIS Breast Cancer Risk Evaluator at the Tyrer-Cuzick laboratory). Evagene is not a medical device.

Diagnostics and counselling: molecular tests, variant reporting, counselling models