Clinicians should have a lower threshold for considering spinal infection as a cause of new or worsening back pain in elderly patients, a Melbourne study has concluded.

Geriatric medicine registrar Dr Sanka Amadoru, from Northern Health, and colleagues found that patients aged 65 or older with spinal infections presented later than younger cases (13 days vs 4 days after the onset of symptoms).

Older patients had fewer typical infective symptoms such as fever, sweats, chills or rigor, but they also had a trend towards higher levels of inflammatory markers, suggesting their infections were more severe.

“When they do present and are treated, they experience poorer outcomes,” Dr Amadoru and colleagues wrote in the Internal Medicine Journal.

Medical treatment was classified as a failure in nine of 34 older patients (26%) compared to only one of 19 younger patients (5%).

“Of the older group, four died during the initial admission, three died after discharge, and two failed antibiotic therapy,” they said. “One of these patients required transfer for neurosurgical intervention, and the other required an extended course of antibiotics alone.”

The younger patient also failed antibiotic therapy and needed neurosurgery.

Diagnoses included discitis/osteomyelitis, facet joint septic arthritis, primary spinal epidural abscess and infection of a spinal prosthesis.

Staphylococcus aureus was the most common of a large number of identified pathogens but, overall, gram-negative bacteria predominated, perhaps as a result of seeding from overt or subclinical bladder or bowel infections.

Dr Amadoru and his colleagues said the vulnerability of older patients, the delayed presentation and atypical symptoms might reflect a range of complicating factors. For example, symptoms could mistakenly attributed to degenerative spinal disease, or presence of delirium or other cognitive impairment might cloud the presentation.

“Another possible reason for later presentation in older people may be that the onset of symptoms is more insidious,” they said.

“Basic investigations (full blood count, C-reactive protein) should be performed in the older patient with new or worsening back pain, even in the absence of classical infective symptoms and signs,” they concluded.

Their findings were based on cases of spinal bacterial infection presenting to The Northern Hospital between 2008 and 2015.