Take actions to bridge the gaps between China and other countries: in the aspect of markers of mineral bone disease from China Dialysis Outcomes and Practice Patterns Study phase 5

Chinese National Renal Data System^[1] is the first national database for Chinese hemodialysis (HD) population, but unfortunately, data of monitoring frequency of laboratory markers were not well recorded, and therapeutic information was not timely updated. So China Dialysis Outcomes and Practice Patterns Study (DOPPS)^[2,3] is a representative of Chinese HD patients with close following, as compared with data of other countries. A total of 1186 patients were enrolled randomly from 45 HD facilities which were also randomly selected from the metropolitan areas in the three largest cities in China (Beijing, Guangzhou, and Shanghai, not in smaller cities or rural areas) from 2012 to 2015. So the study population in China DOPPS cannot be viewed as representative of the whole Chinese HD population, or an updated one. But considering the fact that up to now, a lack of therapeutic medicine was still commonly seen in some hospitals, gaps were significant and more actions were needed, when China DOPPS data were compared with other countries.

This cross-sectional observational China DOPPS phase 5 study from 2012 to 2015^[4] focused on markers of chronic kidney disease-mineral bone disease (CKD-MBD) and management. Prevalences of poor control of MBD markers, such as hypocalcemia (albumin adjusted calcium <8.4 mg/dL, <2.1 mmol/L), severe hyperphosphatemia (phosphorus >7 mg/dL, >1.78 mmol/L), secondary hyperparathyroidism (parathormone [PTH] >600 pg/mL), and vitamin D and phosphate binder prescriptions were compared with other 20 countries. In general, Chinese HD patients were younger, and less likely to be secondary to diabetic kidney disease. Time on dialysis (vintage) in China was shorter than that in Japan.

Although facility directors from 47% of Chinese facilities described upper limit of PTH to be 300 to 399 pg/mL, a relatively stricter target than North America and Europe (but on par with facility directors in Japan), genetic lower PTH,^[5,6] severe secondary hyperparathyroidism in China was still higher than other countries (19% vs. 0–15%). PTH was less frequently measured in China than in other DOPPS regions (3.2% vs. 15.1%–23.2%). Poor control of PTH was not associated with subsequent prescription of active vitamin D, and cinacalcet prescription was rare (2% vs. 16%–24%). Considering genetic lower PTH level of the Chinese population, this calls for more attention to be paid on PTH control (maybe better early control) in China and medication availability.

As the same, 38% Chinese facility directors reported upper phosphorous targets at 5.5 mg/dL or below, targets similar to Europe (lower than those in Japan), but the proportion of patients who have their phosphorous concentration measured monthly was low in China (14.9% vs. >70%). Severe hyperphosphatemia was more common in China than in other countries (27% vs. 7%–10%). Considering lower dietary intake of phosphorous in the Chinese diet,^[7,8] phosphorous in processed foods, snacks, and medication should be paid great attention to.

In the aspect of dialysis adequacy, dialysis session length was shorter in North America. The mean blood flow rate in China was higher than Japan, but lower than North America and Europe. It was noticed that Chinese patients had lower standardized dialysis Kt/V than other DOPPS regions. To reduce severe hyperphosphatemia, better dialyzer, more high flux or hemodiafiltration, more individually dialysis section time might be considered by dialysis center and insurance agency.

While phosphate binders were prescribed to 59% of Chinese patients, the use of drugs, especially that of non-calcium based phosphate binders, was lower than that in other DOPPS countries.

Similar results were identified for calcium. MBD markers were less frequently measured in China than in other DOPPS regions: calcium (15.1% vs. 72.2%–93.3%). Although the prescribed dialysate calcium was higher in China (73% ≥3.0 mEq/L) than other regions, the average concentration of serum calcium (albumin adjusted) in China (9.12 mg/dL) was lower than that in North America and Europe.

Few patients had undergone a parathyroidectomy before DOPPS enrollment in China. Actually, parathyroidectomy might reduce PTH, phosphorous, and calcium levels. This might be an acceptable method to manage high PTH, phosphorous, and calcium.

It should be noticed that, these results were based on the data from 2012 to 2015. Most patients in DOPPS-5 were from year 2012. So this study reflected practice pattern of 7 years ago. After 7 years, there should be some improvements, especially now in China non-calcium based phosphate binders, cinacalcet and paricalcitol become widely used. Bridging the gaps is expected in the near future.

In conclusion, it is time to take actions to bridge the gaps between China and other countries on CKD-MBD. Better practices including standardization of laboratory measurements and treatments in China are expected. Standardization of medication use based on availability and cost is also expected based on the China DOPPS. China-specific guidelines on CKD-MBD with realistic targets based on big data (including China DOPPS) will be developed in the near future.

Conflicts of interest

None.