Japanese researchers developed a noninvasive screening system that uses dried saliva spots to identify patients with spinal muscular atrophy (SMA).

“The sample collection procedure is noninvasive, easy to handle, and requires no hospital visitation,” the authors wrote. Their study was published in the journal Genes and they addressed several advantages to their newly developed method.

To test the method, the authors collected dried saliva spots from 40 SMA patients previously confirmed to carry no SMN1 exon 7 and 21 healthy subjects. One of the samples from the control group failed the analysis.

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The 2 groups had significantly different values (P <.01) of the SMN1/CFTR ratio (SCR). The SCR values calculated for SMA patients and healthy controls were 0.13±0.01 and 0.59±0.12, respectively. These values allowed for the distinction between patients and controls.

However, the tentative cutoff point (0.2) the authors selected to determine the absence of SMN1 was less than the -3 standard deviation of healthy control values (0.23).

Wijaya et al used a modified version of an allele-specific polymerase chain reaction (PCR) methodology, called mCOP-PCR, to detect the SMN1 gene, which is considered the disease-causing gene in SMA. The method used a gene-specific oligonucleotide primer (SMN1-COP) that has a preference for binding to SMN1 rather than to SMN2.

The authors believe that if this method is approved, it may contribute to increasing the SMA diagnosis rate since it could be easily implemented into health checks in schools and workplaces.

“Once dried, DSS samples can be stored at room temperature in the dark, without any special equipment, and they can be sent to a center or a laboratory by airmail, enabling telediagnosis and eliminating hospital visitation,” they explained.

On the other hand, although saliva is currently considered an advantageous source of genetic material, its use is not without limitations (eg, the amount and quality of the DNA recovered from saliva samples).


Wijaya YOS, Nishio H, Niba ETE, et al. Detection of spinal muscular atrophy patients using dried saliva spots. Genes. 2021;12(10):1621. doi:10.3390/genes12101621