Correct classification of chronic kidney disease

As the U.S. population ages, chronic kidney disease (CKD) is becoming more and more prevalent. Some common conditions predispose patients to develop CKD. Recognition and early management of CKD are crucial to limiting progression and reducing the associated morbidity and mortality.

The diagnosis of CKD and documentation of stage are important for correct coding, which affects hospital revenue and severity of illness classification. In addition, reporting the stage of CKD will improve the accuracy of our national health care database, which is important for research and for projections of national health care needs.

Photo by Comstock
Photo by Comstock.

Clinical practice guidelines for CKD have been published by the National Kidney Foundation. The guidelines identify five stages of CKD (see box) based on the glomerular filtration rate (GFR). End-stage renal disease (ESRD) is defined as dialysis-dependent CKD stage 5.

The GFR may be calculated using the Modification of Diet in Renal Disease (MDRD) formula, available on the National Kidney Foundation website. The calculated GFR is proportional to serum creatinine, but also depends on age, race, and gender. Most clinical labs now report calculated GFR together with serum creatinine levels. It is not necessary to perform a 24-hour urine collection to measure creatinine clearance, even though this may be a more precise measure of GFR if done correctly.

The stage of CKD can only be correctly assigned when renal function (and therefore serum creatinine levels) is at a stable baseline. If there is any acute component to a patient's renal disease, wait until renal function is stabilized, or use the prior baseline.

Although the clinical significance and associated risks of CKD begin to accelerate at stage 3, Medicare does not assign significant comorbid status until stage 4 (see box). If the stage is unspecified it won't be considered significant comorbidity. ESRD rarely goes undocumented and clearly represents even greater severity than other stages of CKD.

Always use the currently accepted clinical terminology of “chronic kidney disease” or CKD. Avoid nonspecific, imprecise terminology such as “renal insufficiency” or “chronic renal insufficiency (CRI)” as the appropriate codes for CKD will not be assigned.

In summary, always review the calculated GFR associated with the creatinine level on clinical lab reports. Documentation of any stage of CKD is important; documentation of stage 4 or 5 is crucial for correct coding, hospital reimbursement and classification of CKD patients' severity of illness. Remember, the CKD stage can only be determined when renal function (and creatinine levels) are stable; otherwise, a prior baseline stage can be used for documentation purposes.