Chronic kidney insufficiency affects a significant number of individuals in the developed countries, particularly the United States. The progressive nature of the disease and a substantial reduction in the quality of life over the period of time are the primary reasons why an early diagnosis is crucial. Anemia, progressive bone loss, cardiovascular pathologies such as hypertension and heart failure, as well as dyslipidemia are the most important long-term complications of chronic kidney disease. A complete laboratory workup and determination of the stage of kidney insufficiency are crucial steps in order to optimize treatment and determine the prognosis.
Individuals suffering from chronic kidney insufficiency are at risk of developing cardiovascular, skeletal, and metabolic complications, which is why their quality of life progressively declines over the course of years    . One of the most prevalent signs of chronic kidney insufficiency is anemia, seen in up to 50% of cases  . Anemia stems from the inability of the damaged kidneys to produce erythropoietin, thus promoting various cardiovascular disorders, such as left ventricular hypertrophy, hypertension, angina, and heart failure  . In fact, drowsiness, fatigue, and an overall lack of energy are encountered in the majority of patients, along with pruritus and pain . Dyslipidemia is a frequent finding and contributes to the appearance of cardiovascular diseases, which is the cause of death in up to 40% of cases  . Renal osteodystrophy is a term denoting the pathological changes of the skeletal system that arise in the setting of chronic kidney disease and its four subtypes (osteitis fibrosa cystica, osteomalacia, adynamic bone disease, and mixed osteodystrophy) are responsible for abnormal rates of bone loss and bone growth in these patients, as well as persistent albuminuria and proteinuria . Electrolyte and hormone abnormalities (particularly hyperphosphatemia and changes in the levels of parathyroid hormone, or PTH) arise at later stages and have a severe effect on morbidity  .
The diagnosis of chronic kidney disease may not be easy to attain early on, which is why a thorough laboratory assessment is necessary. Some definitions interpret chronic kidney insufficiency as kidney damage in the presence of reduced albumin levels due to reduced kidney function (estimated by calculating the glomerular filtration rate, or GFR, based on creatinine levels) that persists for at least three months  . For this reason, a complete biochemical workup consisting of serum electrolytes, urea, albumin, and most importantly creatinine, together with urinalysis to evaluate protein loss, is crucial to make the diagnosis . Hyperphosphatemia and hyperparathyroidism are common findings, whereas a complete blood count (CBC) reveals anemia with normochromic and normocytic characteristics, thus excluding causes such as iron or vitamin B12 deficiency . The key step of the workup is to determine the GFR and patients are classified based on the results  :
To make an exact value of the GFR, a 24-hour urine collection of creatinine is used over serum values .