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Measuring iron levels in dogs with SIRS | VETgirl Veterinary CE Podcasts

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In today’s VETgirl online veterinary continuing education podcast, we review the usefulness of measuring iron levels in dogs with systemic inflammatory response syndrome (SIRS). Now, you probably don’t think you see SIRS or septic cases, but you do. SIRS is a result of overstimulation of the inflammatory cascade (with secondary release of inflammatory mediators). SIRS can be seen due to thermal injury (e.g., heat stroke, burns), immune-mediated disease, etc. and can be seen with neoplasia, pancreatitis, trauma, infectious disease, etc. The definition of SIRS is very loose, unfortunately and includes two of the following criteria:

  • Hyperthermia (>39.4 C)
  • Hypothermia (<37.8 C)
  • Tachycardia (>140/min)
  • Tachypnea (>20/min)
  • Neutrophilia (>16.0 × 106 cells/L)
  • Neutropenia (<6.0 × 106 cells/L)
  • Left shift in neutrophils (band cells >3%)

While SIRS is an inflammatory response to sepsis, you can actually fulfill the criteria of SIRS in your own dog by taking him or her for a jog (e.g., tachycardiac, panting). Therefore, keep in mind that it has to depend on the historical findings, clinical signs, physical exam findings, and sources of infection.

Unfortunately, there’s no easy “blood test” for evaluating the outcome with SIRS. There have been a few studies evaluating acute phase proteins (APPs) such as C-reactive protein (CRP), fibrinogen, serum amyloid A, haptoglobin, etc. or what are called “positive APPs” (These are elevated during SIRS). Negative acute phase proteins include albumin and transferrin, and these decrease during SIRS. In real life, it’d be great to be able to have a biomarker that we can easily measure to see if it can be used to help predict mortality or prognosis with SIRS or sepsis. But in real life, a lot of us don’t have the ability to measure CRP easily. So Torrente et al out of Barcelona, Spain wanted to evaluate other parameters that could be evaluated as possible prognostic factors in SIRS in their study “Plasma iron, C-reactive protein, albumin and plasma fibrinogen concentrations in dogs with systemic inflammatory response syndrome.” They specifically wanted to look at iron concentrations in clinical cases of SIRS or sepsis to see if there was any correlation with prognosis.

In this prospective observational study, they evaluated 116 dogs in total, comprising 20 healthy dogs, 54 dogs with SIRS or sepsis, and 42 dogs with what they defined as “focal inflammation.” In all the study groups, blood samples for C-reactive protein, fibrinogen, plasma iron, and albumin were measured on presentation; in the SIRS and focal inflammation group, blood work was then measured every other day until discharge or death. In this study, the median age was 6 years, with approximately a 50% split on male vs. female dogs. In the SIRS group, 79.6% (n=43) of dogs were diagnosed with sepsis, while 20.4% (n=11) were diagnosed with noninfectious SIRS. In the group diagnosed with SIRS and sepsis, they found that the most common source of sepsis was from the abdomen (n=34), followed by three each from the urinary tract, thoracic cavity and skin.

In both the SIRS/septic dogs and local inflammation dogs, they found that iron and albumin concentrations were low, compared to the healthy dogs. By the way, this decrease in iron concentration is hypothesized to be due to hepcidine secondary to inflammatory cytokines. Also, of the two affected groups, they found that dogs with SIRS had a significantly lower iron levels  (65 ± 5.8 μg/dL, P = 0.001) compared to dogs with just focal inflammation (89.5 ± 6.2 μg/dL, P = 0.001). As for C-reactive protein, concentrations were increased in both the abnormal group of dogs as compared to the healthy dogs, with CRP being higher in SIRS/sepsis dogs. For fibrinogen concentrations, they were increased in both abnormal group of dogs; however, there was no difference in the SIRS/sepsis group compared to the local inflammation group.

What they did note was that survivors in the SIRS/sepsis group had a significantly higher plasma iron concentration and lower reduction in CRP concentration as compared to non-survivors. Likewise, as previous studies have also demonstrated, albumin levels were higher in survivors from the SIRS/sepsis group as compared to non-survivors. Overall, this study found that increases in iron concentration and decreases in CRP concentration (from the time of hospital admission to discharge) was higher in survivors than in nonsurvivors within the SIRS/septic group.

So, what can I take from this VETgirl podcast?

As iron levels are more readily available to most veterinarians than C-reactive protein, the evaluation for hypoferremia can potentially be used as a marker for SIRS in dogs. Perhaps looking at this in conjunction with albumin will help us prognostic or help monitor our SIRS /septic patients earlier. If you notice that your SIRS or septic patient has high iron concentrations while in the hospital, this may help you counsel your pet owners on a potentially better prognosis, when evaluated in conjunction with albumin levels.

P.S. One limitation of the study? First, I should disclose that this is not my area of expertise, but was I the only one concerned that hematocrit wasn’t evaluated in this study? Assuming that chronic anemia may be related to iron levels, and that the majority of critically ill patients are often anemic, I thought this might have been an important factor to also look at.

References:

  1. Torrente C, Manzanilla EG, Bosch L, et al. Plasma iron, C-reactive protein, albumin and plasma fibrinogen concentrations in dogs with systemic inflammatory response syndrome. J Vet Emerg Crit Care 2015;25(5):611-619.

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