By Samuel Boye Hinson, Medical Lab Scientist
Across the world and even more in Africa, chronic kidney disease rises quietly. Many people go to the hospital and are reassured that their kidney test results are “normal” only to be diagnosed with chronic kidney disease months or years later. The problem is not always the absence of testing or false results. It is the over reliance on one marker to check kidney functionality; creatinine.
Creatinine is a waste product formed from the normal breakdown creatine in the muscle. Every day, our muscles produce it at a relatively steady rate as we engage them in our day to day activities. Though not inherently toxic, the kidneys filter it from the blood and remove it in urine as most waste substances in the body. Because of this, doctors use blood creatinine levels to estimate how well the kidneys are filtering; a function known as the glomerular filtration rate (GFR). This is then used to estimate kidney damage and efficacy. However, creatinine does not directly measure kidney damage. It only reflects how efficiently the kidneys are clearing this waste product. Factors such as age, sex and muscle mass greatly influence creatinine levels.
A muscular young man may have a “high” creatinine but perfectly healthy kidneys due to his muscles and an elderly or malnourished individual may have a “normal” creatinine despite significantly reduced kidney function. This makes the use of creatinine levels to estimate kidney damage very misleading. The kidneys are remarkably resilient organs. Each kidney contains thousands of filtering units known as nephrons. When some are damaged, the others compensate. Because of this compensation system, up to 50% of kidney function can be lost before creatinine rises above the normal range. This means that kidney disease can silently progress for years while blood results appear to be “normal”. By the time creatinine, the marker, significantly increases, the damage may already be advanced and sometimes irreversible. This is why chronic kidney disease is often called a silent disease.
To address this limitation, laboratories have now adapted something more informative; the estimated Glomerular Filtration Rate (eGFR) which raw adjusts for factors such as age and sex. This provides a more accurate estimate of kidney function. That way, two people can have the same creatinine level but very different eGFR values based on their actual kidney function.
Kidney disease affects the skeleton, the heart, the blood, and the entire metabolic system. Kidney disease does not usually begin with pain or any obvious symptoms. It begins quietly and if we rely on only one marker, we may miss the early whisper before the eventual scream. Early testing, proper interpretation and timely intervention is paramount because when it comes to kidney health, what you don’t see can hurt you.
