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NSA: Serum Proteins (2009)

Citation:

Golner BB, Reinhold RB, Jacob RA, Sadowski JA, Russell RM. The short- and long-term effect of gastric partitioning surgery on serum protein levels. J Am Coll of Nutr. 1987: 6: 279-285.

PubMed ID: 3598025
 
Study Design:
Cohort study.
Class:
B - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

The purpose of this study was to investigate the effects of stress and subsequent low-protein and low-calorie intake on several circulating proteins and the nutrients carried by these proteins at various time points throughout a six-month period after gastric partitioning surgery in obese patients. 

 

Inclusion Criteria:

Patients who were scheduled to undergo elective gastric partitioning surgery for morbid obesity.

Exclusion Criteria:

None noted.

Description of Study Protocol:

Design

  • Baseline fasting blood specimens were drawn on 22 patients prior to gastric partitioning surgery, with follow-up measurements taken at one, three and seven days post-operatively and again at approximately 30, 90 and 180 days post-operatively
  • At each of the time points, the following five serum proteins and micronutritents carried by these proteins were measured: Retinol binding protein levels, transferrin, ceruloplasmin, transthyretin, albumin, iron, copper and zinc. 

Statistical Analysis

The mean of each parameter at each post-operative time point was compared by paired T-test to the pre-operative baseline mean of the corresponding parameter.

Data Collection Summary:

Timing of Measurements

Blood specimens were drawn prior to gastric partitioning surgery (baseline) at one, three and seven days post-operatively, and again at approximately 30, 90 and 180 days post-operatively.

Dependent Variables

  • Variable 1: Retinol levels were determined by reverse phase liquid chromatoggraphy
  • Variable 2: Transferrin levels were measured by rate nephelometry
  • Variable 3: Ceruloplasmin levels were measured by rate nephelometry
  • Variable 4: Transthyretin levels were measured by rate nephelometry
  • Variable 5: Albumin levels were measured by rate nephelometry
  • Variable 6: Iron levels were measured by flame atomic absorption spectroscopy
  • Variable 7: Copper levels were measured by flame atomic absorption spectroscopy
  • Variable 8: Zinc levels were measured by flame atomic absorption spectroscopy.

Independent Variables

Baseline or pre-operative measures of the corresponding dependent variables. 

 

 

Description of Actual Data Sample:
  • Initial N: 22 (19 females, 3 males)
  • Attrition (final N): None reported
  • Age: 23 to 56 years
  • Anthropometrics: All participants were either a minimum of 100 lbs overweight or at a weight that was more than double their reference weight standard
  • Location: USDA Human Nutrition Research Center on Aging at Tufts University, Tufts New England Medical Center, Boston, Massachusetts.
Summary of Results:
  • Serum retinol (figure 1):

    • Serum retinol values were most significantly depressed at days one and three post-operatively (P<0.001 as compared to pre-operative baseline)

    • Decreases in mean serum retinol binding protein virtually paralleled changes in retinol and transthyretin at all post-operative time points during which serum retinol binding protein reached pre-operative levels

    • Serum retinol values were lowest in the period of one to seven days post-operatively (P<0.0001 as compared to baseline) and were only slightly higher (P<0.01) at the remaining time points

  •  Serum iron and transferrin (figure 2):
    • As with all parameters, mean serum iron and transferrin levels were significantly lower than pre-operative levels on the first day post-operatively (P<0.0001)
    • Serum iron and transferrin remained low through post-operative day 30 and transferrin through post-operative day 90 transferrin, but rose thereafter
    • By post-operative day 180, both mean serum iron and transferrin were not significantly different from baseline
  •  Serum copper and ceruloplasmin (figure 3):

    • Serum copper and ceruloplasmin reacted similarly at most time points

    • Both serum copper and ceruloplasmin dropped sharply at post-operative day one (copper P<0.05, ceruloplasmin P<0.01 as compared to baseline)

    • On day three post-operative, mean ceruloplasmin alone was significantly lower than the pre-operative baseline (P<0.05)

    • By post-op day seven, mean ceruloplasmin reached the pre-operative level and mean copper became significantly higher than pre-operative levels (P value not reported)

    • Serum copper and ceruloplasmin mean values fell again by post-operative day 90 (P<0.05 and P<0.01, respectively, as compared to baseline) before becoming non-significantly different from baseline levels at post-operative day 180

  • Serum zinc and albumin (figure 4):

    • Serum zinc reached its nadir on post-operative day one, while albumin reached its nadir on post-operative day three

    • The mean serum zinc level rose to its baseline or pre-operative level by post-operative day seven, while albumin reached  pre-operative levels by day 30

    • Neither mean serum albumin nor zinc levels fell below baseline values at the remaining time points (after day 30).

 

Author Conclusion:
  • The short-half-life proteins, transthyretin and retinol binding protein, are the most sensitive indicators for reflecting protein nutriture in patients who undergo gastric partitioning surgery for morbid obesity
  • The responses of serum ceruloplasmin and transferrin to gradual refeeding show that these proteins are less responsive to lowered protein and caloric intakes
  • The failure of serum albumin to respond negatively to protein calorie deprivation after gastric partitioning surgery indicates that albumin is not a sensitive indicator of protein status in these patients
  • Since serum albumin is used as an indicator of severe malnutrition, the level of protein calorie deprivation experienced by gastric partitioning patients may not result in major malnutrition. 
Funding Source:
Government: USDA Human Nutrition Research Center on Aging, Tufts University, Boston MA
Reviewer Comments:

This study is an older study (1987) and used research methodology was considered less rigorous than today's standards:

  • Funding source(s) were not disclosed
  • Minimal discussion of subject demographics
  • Small sample size
  • Overall clinical outcomes (healing of surgical wounds, weight loss, maintenance of weight loss) were not discussed. 
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) N/A
  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) N/A
 
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? N/A
  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? N/A
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? ???
  2.4. Were the subjects/patients a representative sample of the relevant population? ???
3. Were study groups comparable? N/A
  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? N/A
  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? ???
  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%.) ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? ???
  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? ???
5. Was blinding used to prevent introduction of bias? N/A
  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? N/A
  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? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? ???
  6.6. Were extra or unplanned treatments described? ???
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  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? Yes
  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? Yes
  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? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? ???
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  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)? N/A
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? No
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? No
  10.2. Was the study free from apparent conflict of interest? Yes