Lack of Suspicion by Doctors May Lead to Delayed Diagnosis in SMA

Clinicians disregard, misinterpret symptoms reported by parents: study

Steve Bryson, PhD avatar

by Steve Bryson, PhD |

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A delayed diagnosis in spinal muscular atrophy (SMA) may occur in many cases due to the absence of clinical suspicion of the rare genetic disorder, an interview-based study concluded.

In particular, treating physicians of pediatric patients often disregarded or misinterpreted signs reported by parents, leading to diagnostic delays, the researchers said.

“It is particularly relevant to raise awareness among physicians who provide primary care to patients of these ages through medical education programs focusing on early recognition and diagnosis of SMA and other neuromuscular diseases,” the team wrote.

“Shortening diagnostic times is critical for current therapies to be successful,” they added, noting that “neonatal SMA screening programs have great potential to identify affected children.”

The study, “The difficult path to diagnosis of the patient with spinal muscular atrophy,” was published in the journal Archivos Argentinos de Pediatria.

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Knowing diagnostic requirements

SMA is classified into subtypes according to age at onset and severity of symptoms. Clinical signs of SMA can vary widely, and some symptoms — such as low muscle tone and motor delays — are common to other neuromuscular conditions as well. As a result, a delayed diagnosis is common.

Now, researchers in Argentina attempted to reconstruct the path to diagnosis experienced by people with SMA and explore some of the leading causes of diagnostic delay.

“Our study is the first of its kind in Argentina and provides data about the age at onset of first signs and delays in diagnosis,” the researchers wrote.

The team recruited 112 patients with SMA, ages 10 months to 38 years. Among them, 40 were recently diagnosed with SMA type 1, and 48 with SMA type 2 — both typically identified in young children. A total of 24 patients had SMA type 3, usually a milder form.

Neurologists who specialize in neuromuscular diseases conducted face-to-face or telephone interviews with patients and/or their relatives and collected various data regarding their path to diagnosis.

Among those with SMA type 1, the time from first signs to a confirmed diagnosis was shorter — a median of one month — for those born more recently, from 2018 to 2020. That compared with a median 2.5 months to diagnosis for patients born from 2005 to 2018. This was due to the increased availability of diagnostic molecular tests in Argentina in recent years, the researchers noted.

First signs of SMA type 1 were noted by parents in 29 cases (72.5%), grandparents in three cases (7.5%), a pediatrician in five (12.5%), and a neonatologist in two cases (5%). A multidisciplinary team of physicians identified one patient (2.5%) with type 1.

Parents noticed SMA type 2 signs in 41 cases (85%). First symptoms were noted by grandparents in five type 2 patients (10.4%), while aunts or uncles first saw signs in two cases (4.2%).

In SMA type 3, parents noted symptoms in 18 cases (75%), and other relatives, or patients themselves, in one case each (4.2%). In two instances (8.3%), teachers first reported the signs.

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Less frequent medical checkups are a factor

Among 72 participants — 48 with SMA type 2 and 24 with type 3 — for whom routine medical checkups were less frequent than in the first months of life, only one physician was able to note the first signs of the condition.

A pediatrician was the most frequently visited specialist at the first consultation, which included 33 SMA type 1 patients (82.5%), 46 SMA type 2 individuals (95.8%), and 16 with SMA type 3 (66.6%). Until clinical suspicion of disease, the median number of consultations was three for SMA type 1 patients (range one to six), four for SMA type 2 (range two to 15), and four for type 3 (range two to 11).

SMA type 1 patients consulted a variety of different specialists, including pediatricians, neurologists, a multidisciplinary team, clinical geneticists, pulmonologists, and an obstetrician. For type 2 patients, pediatricians, neurologists, traumatologists, clinical geneticists, endocrinologists, and a kinesiologist, were consulted. Similar findings were seen for SMA type 3 patients.

A diagnostic molecular study was requested for SMA type 1 patients by a neurologist in 33 cases (82.5%), by a multidisciplinary team in six cases (15%), and in one case, by a geneticist (4.2%). For SMA type 2, 22 patients (95.8%) underwent a molecular study as required by a neurologist and a geneticist in two cases (4.2%). SMA type 3 molecular studies were directed by neurologists in 22 cases (91.7%) and by a geneticist in one patient (4.2%).

Additional testing included electromyography, which assesses muscle function, brain ultrasound, and brain and spinal MRI. Chest/hip X-ray, brain CT scan, muscle/nerve biopsy, and a video swallowing exam were done for other patients. Also, patients underwent chromosome testing, electroencephalogram that examines brain waves, lumbar puncture, and various blood tests.

Genetic studies were initially requested in nine SMA type 1 patients (22.5%), and eight SMA type 2 individuals (16.7%). None were requested in the SMA type 3 group.

“The cause of delay in diagnosis is mainly the lack of clinical suspicion on the part of the intervening physician, who often disregards or misinterprets signs reported by parents, as
reflected in the alternative diagnoses,” the team wrote.

“There are also significant delays from clinical suspicion to confirmed diagnosis, especially in types [2] and [3]. In SMA [1], the onset is earlier and more striking: hence, the diagnostic process is faster,” the researchers wrote.