Creatinine, a key urine marker tested by Quest Diagnostics, is an important indicator of kidney function and overall renal health. It is a waste product produced by the normal metabolism of muscle tissue and is usually filtered out of the blood by the kidneys and excreted in urine.

The measurement of creatinine levels in urine is a critical component of various health assessments, particularly in evaluating kidney function. Urine creatinine helps in diagnosing kidney diseases and monitoring the effectiveness of treatment for renal disorders. The concentration of creatinine in urine can reveal how well the kidneys are functioning; unusually high or low levels can indicate renal impairment or disease. This test is often used in conjunction with other tests, such as blood creatinine levels and the calculation of creatinine clearance, to provide a more comprehensive view of kidney health.

Additionally, urine creatinine levels are used to normalize the levels of other substances in urine, providing more accurate results for tests such as urine protein. This is particularly important in drug testing, where creatinine levels are measured to ensure that urine samples have not been diluted, which could mask the presence of drugs. 

Creatinine values are measured to correct results for urine dilution.

Creatinine is a waste product produced by muscles from the breakdown of a compound called creatine. Creatinine is filtered from the blood by the kidneys and released into the urine.

The amount of creatinine produced in the body is dependent on muscle mass and is relatively constant for an individual. The amount of creatinine removed from the blood depends on both the filtering ability of the kidneys and the rate at which blood is carried to the kidneys.

The biomarker Creatinine-Corrected Urine Iodine is an essential measure in evaluating iodine levels in the body, normalized against creatinine levels in urine. This correction accounts for variations in urine concentration, making the results more accurate for assessing iodine status across different hydration levels.

What Is Iodine and Why Is It Important?

Iodine is a vital micronutrient required for the production of thyroid hormones, which regulate metabolism, growth, and development. Adequate iodine intake is particularly crucial during pregnancy, infancy, and childhood to support brain development and prevent thyroid dysfunction.

Why Correct for Creatinine?

Creatinine is a waste product of muscle metabolism, excreted at a relatively constant rate in urine. By correcting iodine levels against creatinine, the test provides a more reliable measure of iodine status, independent of factors like fluid intake or urine dilution.

Crenated erythrocytes are red blood cells (RBCs) with an irregular, spiked appearance caused by cellular dehydration or exposure to hypertonic environments. In cerebrospinal fluid (CSF), their presence typically reflects structural damage or mechanical disruption to blood vessels, leading to RBC breakdown or abnormal morphology.

CRP/ESR Ratio is a calculated value that compares levels of C-reactive protein (CRP) to the erythrocyte sedimentation rate (ESR)—two common markers used to detect inflammation in the body. This ratio can provide deeper insight into the type and intensity of inflammation, helping to distinguish between different causes of inflammatory responses.

What Do CRP and ESR Measure?

• C-reactive protein (CRP) is a protein produced by the liver in response to acute inflammation. Its levels rise quickly within hours of tissue injury or infection.

• Erythrocyte Sedimentation Rate (ESR) measures how quickly red blood cells settle at the bottom of a test tube in one hour. It increases more slowly and reflects more chronic or long-term inflammation.

Cryoglobulins are circulating proteins, specifically immunoglobulins (i.e., IgG, IgM, IgA or light chains), that clump together (precipitate) when they are exposed to cold and dissolve when warmed. They may be present in small quantities in the blood of some healthy people but are most frequently associated with abnormal protein production and a variety of diseases and conditions. This test detects and measures the relative quantity of cryoglobulins in the blood.

C. parvum is a protozoan parasite that can cause gastrointestinal illness with diarrhea in humans. Through various mechanisms the parasite can manipulate the host cytoskeleton proteins, including rearranging tropomyosin-5 protein, actinin, villin, ezrin, at the site of infection. This restructuring of proteins allows the parasite to infiltrate intestinal cells. Due to antigenic similarity between C. parvum, actin and tropomyosin structures, these antibodies may cross-react with human tissues resulting in autoimmunity associated with parasitic infections.

Cryptosporidium is notorious for being spread by swimming pools. A number of Cryptosporidium outbreaks have occurred after contamination of public swimming facilities. Cryptosporidium can cause gas, bloating, diarrhea, and abdominal pain. In a healthy, immune-competent person, this is a selflimiting infection and can be cleared within 2-3 weeks.

The Cryptosporidium parasite causes disease in humans through ingestion of infectious oocysts in contaminated water or food, and by direct contact with fecal material from individuals or animals actively shedding oocysts. Two species of Cryptosporidium cause disease in humans, Cryptosporidium hominis and Cryptosporidium parvum. C. hominis is more prevalent in the US, South America, Australia, and Africa, while C. parvum accounts for most cases in Europe. Along with Giardia, Cryptosporidium is the most common parasitic cause of diarrheal illness in the US and other developed nations.

Cryptosporidiosis is a disease that causes watery diarrhea. Crypto is caused by a microscopic parasite called Cryptosporidium. Anyone can get sick with Crypto, but people with weakened immune systems are more likely to have severe and potentially life-threatening symptoms. This includes people who have health problems or take medicines that lower their body’s ability to fight germs and sickness—such as people whose immune systems are weakened because of cancer, an organ transplant or have cancer, or HIV.