Is symmetric dimethylarginine superior to creatinine for assessing glomerular filtration rate for cats with kidney disease?

PICO question Is symmetric dimethylarginine (SDMA) superior to creatinine for assessing glomerular filtration rate (GFR) for cats with chronic kidney disease?   Clinical bottom line Category Diagnosis.   Number and type of studies reviewed: The literature searches returned four relevant papers that answered this PICO. Three of the studies were retrospective diagnostic test studies, and one was a randomised, controlled, unblinded study.   Strength of evidence Moderate.   Outcomes reported Three out of the four studies analysed found that there was no significant difference between the correlation between symmetric dimethylarginine (SDMA) and glomerular filtration rate (GFR) and creatinine (sCr) and GFR, whilst the other identified a stronger correlation between SDMA and GFR. Two papers also evaluated the sensitivity and specificity of SDMA compared to creatinine. One paper found a similar sensitivity for both biomarkers and a significantly higher specificity for creatinine using the upper reference interval of 18 µg/dL for SDMA and 155.6 µmol/L (1.76 mg/dL) sCr, whilst the other found SDMA to have a superior sensitivity and both biomarkers to have a similar specificity using the upper reference interval of 14 µg/dL for SDMA and 185.64 µmol/L (2.1 mg/dL) for sCr.   Conclusions In view of the strength of evidence we conclude that the majority of the studies analysed do not demonstrate that SDMA is superior to creatinine for the assessment of GFR in cats with chronic kidney disease. More research is needed with larger sample sizes to investigate this further. Standardisation of the upper reference intervals across studies for creatinine and SDMA would be advantageous for comparison of sensitivity and specificity in future studies.   How to apply this evidence in practice The application of evidence into practice should take into account multiple factors, not limited to: individual clinical expertise, patient’s circumstances and owners’ values, country, location or clinic where you work, the individual case in front of you, the availability of therapies and resources. Knowledge Summaries are a resource to help reinforce or inform decision making. They do not override the responsibility or judgement of the practitioner to do what is best for the animal in their care.