EAL

CKD: Nutrition Assessment and Best Predictors of CKD (2001)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

The purpose of this study, as an extension of previous analysis by the authors, was to compare the relative risks of mortality of prealbumin with that of other nutritional markers in a cohort of dialysis patients.

Inclusion Criteria:

Hemodialysis (HD) or peritoneal dialysis (PD) patients enrolled in study between June 1991 and March 1992 at Long Island College Hospital, Brooklyn, NY.

Exclusion Criteria:

Known HIV positive patients.

Description of Study Protocol:

Recruitment: method not mentioned

Design: Cohort Study. Patients followed from time of enrollment up to death, switch in dialysis modality, renal transplant, transfer, or May, 1996 (5 year maximum follow up).

Blinding used: not applicable - lab tests

Intervention: not applicable

Statistical analyses: SPSS Windows version 7.0.

Multivariate repeated measures ANOVA and chi-squared for comparisons between groups (HD vs PD).
Kaplan-Meier life table method to analyze observed patient survival between groups.
Cox proportional hazards model to determine independent predictors of mortality, adjusted for confounding factors.
Spearman rank coefficients to determine correlation between variables.

Data Collection Summary:

Timing of measurements:

Chart review during the course of the study for demographic and biochemical data, including: age, race, gender, diabetic status, cause of ESRD and total months on dialysis at time of enrollment.

Biochemical data collected at enrollment (baseline): total cholesterol + SMAC, prealbumin, and blood urea nitrogen

Dependent variables: death

Independent variables: serum prealbumin at baseline

Control variables:

age, race, gender, diabetes
serum albumin, creatinine, cholesterol
prior months on dialysis

Dialysis prescription:

HD: treated on Cobe Centry System 3 machines with bicarbonate-based dialysate and volumetric ultrafiltration control; targeted urea reduction ratio was >60% and validated by monthly blood sampling performed on the first treatment of the week.

PD: four 2-liter exchanges/d; weekly creatinine clearance was initially estimated by extrapolating the 4-hr peritoneal equilibration test and adjustments were made to maintain a creatinine clearance > 50 L/wk/1.7 m².

Description of Actual Data Sample:

Initial N: HD:111, PD:78

Causes of ESRD were hypertension, 36%, diabetes, 34%, polycystic kidney disease, 8%, glomerulonephritis, 7%, and other, 15% in the HD group, similar results were seen in the PD group.

Attrition (final N): none mentioned

Age, Ethnicity, Other Relevant Demographics:

Demographics, (mean+SD)
	HD (n=111)		PD (n=78)
	No.	%	No.	%
Age (yr)	59.9+15.5		54.0+15.9

Race:
White	30	27	18	23
Black	61	55	41	53
Hispanic	20	18	19	24

Male	54	49	34	44
Female	57	51	44	56

Diabetes:
Yes	42	38	28	36
No	69	62	50	64

Prior months on dialysis	56+51		78+11

Anthropometrics: none mentioned

Location: Long Island College Hospital, Brooklyn, New York

Summary of Results:

Mean patient survival after enrollment: 2.91 years.

**Biochemical Profile of Subjects:**
	% of subjects
Albumin, g/dL	HD	PD
< 3.5	14	38
> 3.5	86	62
Creatinine, mg/dL
< 9	20	26
> 9	80	74
Cholesterol, mg/dL
< 200	76	38
> 200	24	62
Prealbumin, mg/dL
< 30	67	32
> 30	33	68

When indices were analyzed separately, low prealbumin levels showed the greatest correlation with increased mortality risk in the HD group. Low creatinine levels imparted greater risk in both groups. Low albumin imparted greater risk for the PD group:


Predictive value of death by enrollment levels	HD		PD
	n=111		n=78
	Relative Risk	P	Relative Risk	P
Albumin (g/dL) <3.5 vs. >3.5	1.47	0.26	2.1	0.019
Creatinine (mg/dL) < 9 vs. >9	2.0	0.035	2.7	0.003
T cholesterol (mg/dL) <200 vs. >200	1.73	0.073	0.98	0.96
Prealbumin (mg/dL) <30 vs. >30	2.64	0.002	1.8	0.035

Using the Cox proportional hazards analysis, in which adjustments are made for confounding variables, the following were independently predictive of higher mortality up to 5 years:


HD patients: (n=111)	Relative Risk	P
Age	1.03	0.004
Diabetic status	1.77	0.05
Prealbumin (<30 mg/dL)	2.32	0.011


PD patients: (n=78)	Relative Risk	P
Age	1.05	0.001
Diabetic status	2.59	0.006

Author Conclusion:

In this study, the level of serum prealbumin at enrollment is the single strongest predictor of 5-yr survival in these HD patients. Serum prealbumin also significantly predicts survival at 5 years in PD patients. Serum prealbumin levels correlated significantly with other measures such as albumin, creatinine, and cholesterol.

Serial measurement of serum prealbumin levels may therefore be included in designing of interventions to improve nutritional status in ESRD patients. In addition, the serum prealbumin level may be useful to identify patients at risk of near term death, signaling the need for appropriate intervention.

Funding Source:

University/Hospital:

The Long Island College Hospital

Not-for-profit

Foundation associated with industry:

Reviewer Comments:

The significance of this study was that baseline prealbumin level < 30 mg/dL was a strong predictor for death in HD subjects.

The authors do not explain why subjects received either HD or PD. Measurements at baseline were used as potential predicators of mortality, there were no measures reported during follow up to determine progression in status. No weight, height or BMI measures were reported.

No statistics were reported to compare between the groups.

No explanation was given as to why prealbumin was such a strong predictor in the HD group, but not a predictor in the PD group. Diabetes was most predictive of mortality in this group of PD subjects. Although the authors state that low prealbumin at baseline was predictive of death in the PD group, the statistics do not support this statement.

Not clear why low serum creatinine level would be an indicator of increased risk for mortality (vs high serum creatinine).

Quality Criteria Checklist: Primary Research
Relevance Questions
	1.	Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies)	???
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	3.	Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice?	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	???

Validity Questions
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
2.	Was the selection of study subjects/patients free from bias?		Yes
	2.1.	Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	Yes
	2.4.	Were the subjects/patients a representative sample of the relevant population?	Yes
3.	Were study groups comparable?		No
	3.1.	Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	N/A
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	N/A
	3.4.	If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis?	No
	3.5.	If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.)	N/A
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	N/A
4.	Was method of handling withdrawals described?		No
	4.1.	Were follow-up methods described and the same for all groups?	???
	4.2.	Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.)	No
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	No
	4.4.	Were reasons for withdrawals similar across groups?	???
	4.5.	If diagnostic test, was decision to perform reference test not dependent on results of test under study?	N/A
5.	Was blinding used to prevent introduction of bias?		Yes
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	N/A
	5.2.	Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.)	Yes
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	Yes
	5.4.	In case control study, was case definition explicit and case ascertainment not influenced by exposure status?	N/A
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	N/A
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		???
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	???
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	No
	6.4.	Was the amount of exposure and, if relevant, subject/patient compliance measured?	???
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	No
	6.6.	Were extra or unplanned treatments described?	No
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	???
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	N/A
7.	Were outcomes clearly defined and the measurements valid and reliable?		???
	7.1.	Were primary and secondary endpoints described and relevant to the question?	Yes
	7.2.	Were nutrition measures appropriate to question and outcomes of concern?	???
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	Yes
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	Yes
	7.5.	Was the measurement of effect at an appropriate level of precision?	???
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	No
	7.7.	Were the measurements conducted consistently across groups?	???
8.	Was the statistical analysis appropriate for the study design and type of outcome indicators?		???
	8.1.	Were statistical analyses adequately described and the results reported appropriately?	???
	8.2.	Were correct statistical tests used and assumptions of test not violated?	???
	8.3.	Were statistics reported with levels of significance and/or confidence intervals?	Yes
	8.4.	Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)?	N/A
	8.5.	Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)?	Yes
	8.6.	Was clinical significance as well as statistical significance reported?	No
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
9.	Are conclusions supported by results with biases and limitations taken into consideration?		No
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	No
10.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes