Objectives

Lymphocyte percentage (LYM%), an independently measured value to reflect peripheral lymphocyte count and a possible nutritional marker, may be related to clinical outcome in maintenance dialysis (MHD) patients.

Study design and setting

We examined the associations of the baseline white blood cell count (WBC) and LYM% with 12-month mortality and three measures of hospitalization in a cohort of 1,283 MHD patients from 10 outpatient DaVita dialysis clinics in Los Angeles County, as well as in a subcohort of 372 MHD patients with additional measures of inflammation, nutrition and comorbidity. Multi-variate Cox and Poisson models that included 13 co-variates including case-mix features, dialysis dose, blood hemoglobin and serum albumin were explored.

Results

Patients, aged 57.8 +/- 15.2 years, included 49% men and 49% diabetics. Baseline WBC was 7,353 +/- 2.427 per microl, and LYM% was 21.2 +/- 7.3%. LYM% had significant correlations with "malnutrition-inflammation score" and inverse correlations with serum interleukin-6. The WBC and LYM% had significant but opposite predicting values for mortality and hospitalization, indicating that a high WBC and a low LYM% were each independently associated with increased mortality. After dividing each variable into four quartiles, only the highest WBC quartile (> or = 8,500) but not the other middle two quartiles, predicted increased mortality. However, all three lower quartiles of LYM% vs. the highest quartile (based on quartile cutoffs of 16%, 20.3% and 25.5%) were significantly and progressively associated with greater risks of mortality and hospitalizations. The absolute lymphocyte count (LYM% times WBC/100) exhibited somewhat similar trends but its outcome predictability was not as strong as LYM%.

Conclusions

A high WBC and a low LYM% are associated with significant increase in mortality and hospitalization in MHD patients. Lymphocyte percentage, compared to absolute lymphocyte count, appears to be a better nutritional and anti-inflammatory marker and a more sensitive predictor of mortality and hospitalization in MHD patients.

Although renal osteodystrophy and vitamin D analogs may be related to survival in maintenance hemodialysis (MHD) patients, most studies have examined associations between baseline values and survival without accounting for variations in clinical and laboratory measures over time. We examined associations between survival and quarterly laboratory values and administered paricalcitol in a 2-year (July 2001-June 2003) cohort of 58,058 MHD patients from all DaVita dialysis clinics in USA using both time-dependent Cox models with repeated measures and fixed-covariate Cox models with only baseline values. Whereas hypercalcemia and hyperphosphatemia were robust predictors of higher death risk in all models, the association between serum calcium and mortality was different in time-varying models. Changes in baseline calcium and phosphorus values beyond the Kidney Disease Outcome Quality Initiative recommended targets were associated with increased mortality. Associations between high serum parathyroid hormone and increased death risk were masked by case-mix characteristics of MHD patients. Time-varying serum alkaline phosphatase had an incremental association with mortality. Administration of any dose of paricalcitol was associated with improved survival in time-varying models. Controlling for nutritional markers may introduce overadjustment bias owing to their strong collinearity with osteodystrophy surrogates. Whereas both time-dependent and fixed-covariate Cox models result in similar associations between osteodystrophy indicators and survival, subtle but potentially clinically relevant differences between the two models exist, probably because fixed models do not account for variations of osteodystrophy indices and changes in medication dose over time.