We initiated the Pre-fALS study in 2007 as a systematic attempt to assemble and longitudinally follow a cohort of individuals at genetic risk for ALS. Pre-fALS is approved by the University of Miami institutional review board; all participants have provided informed consent. The explicit goals of Pre-fALS are to 1) characterize the presymptomatic phase of ALS using a wide range of biomarkers; 2) ascertain the incidence rate with which at-risk individuals progress to manifest disease; 3) explore potential genetic and environmental modifiers of the timing of progression to manifest disease; 4) establish a biobank of rigorously collected biological samples for “wet” biomarker discovery; and 5) use the knowledge gained to facilitate design of a preventive/early therapeutic trial. The Pre-fALS protocol has evolved since its inception to allow for adaptation to new scientific advances and development of new biomarkers, as well as input from the scientific and fALS community. The scope of Pre-fALS has also broadened in response to the identification of new genetic causes of ALS. The underlying goals, design, and approach, however, have remained unchanged. Here we use Pre-fALS (NCT00317616) as an example to illustrate how one might approach the aforementioned challenges.
Identifying an at-risk population.
The relative rarity of fALS has led us to identify and enroll pedigrees (, #1) from across the United States using both passive and active recruitment strategies. Before enrolling unaffected family members, we first determine the genetic cause of ALS in the family by testing (or obtaining results of prior testing from) an affected individual or an obligate carrier (, #2). When Pre-fALS first began, we only included SOD1 families, as SOD1 was at the time the only known (and relatively common) cause of ALS. We have since expanded Pre-fALS to include also families with more recently identified mutations (e.g., TARDBP, FUS, VCP, C9ORF72). Parenthetically, we use the term Pre-fALS study (or Pre-fALS for short) to encompass the extensive screening process to identify presymptomatic gene carriers; the term Pre-fALS
cohort is reserved for the subset of Pre-fALS participants who are subsequently enrolled in longitudinal follow-up.
Pre-Symptomatic Familial ALS study schema showing recruitment of presymptomatic individuals from familial amyotrophic lateral sclerosis pedigrees in which the genetic cause of amyotrophic lateral sclerosis is known
Once the genetic cause of ALS in the family is known, unaffected family members may be considered for Pre-fALS (, #3). We focus enrollment efforts on these first-degree relatives because they have the highest likelihood of having inherited the mutated gene, and genetic counseling is more readily performed for them. Moreover, this targeted recruitment approach provides an “enriched” study population, thereby maximizing our likelihood of identifying presymptomatic gene carriers for the Pre-fALS cohort. To date, no eligible individuals have declined participation.
After additional screening (e.g., for psychosocial readiness), those who are known to be gene mutation carriers through previous genetic testing are enrolled directly into the Pre-fALS cohort (, #4). Participants who do not know their genetic status are offered testing and the option of whether or not to learn the results (, #5); we refer to these as the “disclosure” and “nondisclosure” groups, respectively. Predecision counseling is provided as needed to help participants choose between disclosure and nondisclosure of results. Those who elect disclosure receive both pretest and post-test counseling (, #6) and are informed of the results; only gene mutation carriers are enrolled in the Pre-fALS cohort (, #7). Because obligate carriers do not always know that they carry the mutated gene, they too may receive genetic counseling before entering the Pre-fALS cohort. The nondisclosure group comprises a mixture of presymptomatic gene carriers and noncarriers (who may serve as controls in some of our biomarker studies). In order to avoid implicit disclosure of results, all participants who elect nondisclosure are enrolled in the Pre-fALS cohort, irrespective of genetic results (, #8).
Ethical, legal, and psychosocial considerations.
is a single-center study with participants recruited from across the United States raises the question of how best to provide adequate counseling for those who elect to learn their test results. During the first 3 years of Pre-fALS
, participants who elected disclosure were randomized to receive counseling either via telephone or in person. The findings38
highlight the strengths and weaknesses of each approach and provided proof-of-principle that genetic counseling could adequately be performed remotely, at a significantly reduced logistical burden and cost. Based on these results, Pre-fALS
procedures were modified such that counseling is by default provided telephonically, though participants may choose in-person counseling. Following pretest counseling, Pre-fALS
participants may change their minds and elect instead not to learn their results. Similarly, those who initially elect nondisclosure have the option to learn their results at any stage after receiving appropriate genetic counseling.
A series of measures have been adopted to safeguard the confidentiality of genetic test results. Despite the challenges in the era of electronic medical record, research records are strictly separated from medical records. DNA samples are assigned an ID number that requires complex linkage to identifiable information, and all research personnel who have contact with study participants are blinded to the results of genetic testing for nondisclosure participants. In addition, we operate under an NIH certificate of confidentiality, which enables us to provide study participants with a legally enforceable guarantee of research record protection.
As part of the consenting process, participants are counseled that they will be informed if evidence of ALS is detected. The significance of early cognitive/behavioral symptoms is discussed in the context of specific gene mutations. This approach respects participants' right to know and affords the opportunity to initiate early treatment and participation in therapeutic trials.
Telephone counseling has been used to overcome the logistical challenge of counseling those residing great distances from the study center. In addition, completing the array of study procedures performed at each in-person visit (outlined in the next section) requires careful coordination to ensure collection of biological samples in the fasting state, avoidance of lumbar puncture <24 hours prior to air travel, and availability of both equipment (e.g., MRI) and study staff with expertise in a diverse range of biomarker techniques. We currently schedule in-person visits every 12–18 months, and provide quarterly telephone interviews in between visits to ascertain the emergence of symptoms that might suggest the appearance of manifest disease. Participants are also urged to contact the study center at any time if they become aware of worrisome symptoms, which in turn prompt an ad hoc in-person visit for more detailed evaluation. In addition, we maintain contact with participants through telephone calls and a regular newsletter.
Methods for detecting presymptomatic disease.
The presymptomatic phase of ALS is anchored by disease onset and the appearance of motor manifestations. We use the revised El Escorial diagnostic criteria for fALS (progressive UMN or LMN signs in an individual with an ALS susceptibility gene mutation) to define clinically manifest disease based on careful examination by the same ALS specialist (M.B.) at each in-person visit. During the first 3 years of Pre-fALS
, a second neurologist also performed independent evaluations, with complete agreement between the 2 neurologists in determining the presence/absence of clinically manifest disease. In light of the emerging connection between ALS and FTD, especially in families with FUS
, and C9ORF72
mutations, detailed cognitive/behavioral testing has been added to the battery of evaluations. Supine and erect vital capacities are compared to detect subtle diaphragmatic weakness. Electromyographic examination of cranial, thoracic paraspinal, and limb muscles bilaterally is used to test for subclinical LMN dysfunction. Recognizing the need to explore a broad range of investigative modalities potentially sensitive to early manifestations of the disease process, this core set of evaluations is currently supplemented by biomarkers that aim to quantify UMN and LMN function: LMN numbers innervating hand and foot muscles are estimated using the modified incremental MUNE technique;39
multi-frequency electrical impedance myography, which quantifies the biomechanical properties of muscle,40
is employed to study muscles in both arms and legs; evidence of UMN pathology is sought using whole-brain and spinal cord MRS and DTI; fine quantitative motor testing41
provides an integrated view of UMN and LMN function. Finally, a range of biological samples (serum, plasma, DNA, RNA, buffy coat, urine, and, when possible, CSF and cell lines) are rigorously collected, processed, and stored for future “wet” biomarker discovery.