New index, dubbed PINI, may help predict risk of death in AAV: Study

As clinical tool, PINI could help in guiding patient care

Marisa Wexler, MS avatar

by Marisa Wexler, MS |

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The prognostic immune nutritional index or PINI — a novel clinical tool based on counts of immune cells and levels of a blood protein called albumin — can be used to help predict the risk of death in people with ANCA-associated vasculitis (AAV), a new study shows.

For serious diseases like AAV, such prognostic indexes — ones that can predict the risk of severe outcomes — may be useful for guiding patient care, according to researchers.

“PINI could be a clinically relevant indicator in the prognostication of patients with AAV and aid in providing optimal management,” the team wrote.

As of now, the Five-Factor Score (FFS) and the Birmingham Vasculitis Activity Score (BVAS) are used to predict outcomes in people with AAV. But the FFS is based on certain clinical features that may “overlook overall disease status,” the researchers wrote, while BVAS “relies on the clinician’s interpretation,” which may vary between health care providers.

Their findings on PINI were detailed in a new study, “A prognostic immune nutritional index can predict all-cause mortality in patients with antineutrophil cytoplasmic antibody-associated vasculitis,” published in Therapeutic Advances in Musculoskeletal Disease

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New index can predict mortality at AAV diagnosis in non-obese patients

Seeking better outcome predictors, including for risk of death, in AAV

While various indexes such as FFS and BVAS already exist for predicting disease outcomes among AAV patients, researchers have been working to identify new and better tools for assessing risk. Earlier this year, a South Korean team identified a new index that can predict all-cause mortality in non-obese people with AAV.

Now, scientists at Yonsei University College of Medicine, in Seoul, assessed the prognostic potential of a novel risk score called the prognostic immune nutritional index, dubbed PINI.

“Studies have proposed that nutritional and immune-related markers are relevant with patient outcomes of various medical conditions and could be a useful indicator of patient prognostication,” the researchers wrote.

The team tested PINI in 250 people with AAV.

It is a readily available measure that could be simply assessed during routine laboratory testing.

The index incorporates two measures: number of monocytes, a type of immune cell, and levels of the blood protein albumin, which helps to carry certain nutrients through the bloodstream.

“It is a readily available measure that could be simply assessed during routine laboratory testing,” the team wrote.

The patients were participating in an observational study of Korean AAV patients at Severance Hospital in South Korea between 2000 and 2022. Their median age at the time of diagnosis was 60 and more than half (54%) had microscopic polyangiitis, the most common type of AAV. About one-third of the participants were men.

Over a median follow-up of more than three years, 13.2% of the patients died. Additionally, 16.8% developed end-stage renal disease (ESRD), or kidney failure, over a median follow-up time of more than two years.

Lower PINI scores were significantly associated with older age and higher levels of inflammatory markers such as total immune cell counts.

Statistical models showed that patients with a PINI score of 2.47 or lower were more than four times more likely to die during follow-up. At this cutoff value, PINI could accurately identify 75% of patients who died and 61% of those who did not die.

Similarly, patients with a PINI score of 3.12 or lower were nearly three times as likely to develop kidney failure. This cutoff accurately identified 46% of patients who developed ESRD and 79% of those who did not.

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1-Year Mortality Rate in AAV Found Higher in Men Than in Women

PINI scores at diagnosis may suggest ‘a precaution is needed’

Models adjusted for multiple potential influencing factors showed that all-cause mortality was significantly higher in older patients, men, individuals with higher FFS and BVAS scores — which indicated a worse prognosis — and those with a PINI score of 2.47 or lower.

However, of the three prognostic measures, only FFS was independently associated with the risk of kidney failure in these models.

“PINI may be clinically useful, as the [statistical models] revealed that PINI was associated with patient mortality even when BVAS and FFS – a traditional measure that is considered to have an association with patient prognosis in AAV – was included as a [influencing factor],” the researchers wrote.

“PINI could be a potential laboratory marker indicating adverse clinical outcomes, suggesting a precaution is needed in those with PINI [scores up to 2.47] at diagnosis,” they added.

Given that most of the reported deaths were associated with disease activity, pneumonia, and other lung diseases, regular monitoring of chest X-rays and respiratory symptoms among patients with low PINI scores may “improve patient outcome of mortality,” the team wrote.

They noted, however, that this study was limited by its retrospective and single-center nature, highlighting a need for further research to evaluate the utility of this marker in a broader patient population.

“We believe that an external validation by its application in independent [groups of patients] and [follow-up] studies would better verify our results and provide insights in whether PINI are useful in predicting outcomes of patients with AAV,” the researchers concluded.