EAL

HYD: Assessing Hydration Status (2007)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

A: measurements of total body water via deuterium oxide dilution and BIA

B: to identify physiological and anthropometric predictors of physical performance during uniformed exercise in a hot environment.

C: to measure fluid-electrolyte balance of collegiate tennis players during 3 tennis matches, played over 10-hr period, in a hot environment.

Collectively: To determine if urine color (Ucol) indicates hydration status accurately. The 3 experiments used a novel Ucol scale and assessed corresponding urinary and hematologic measurements.

To clarify the interchangeability of Ucol, urine osmolality (Uosm) and urine specific gravity (Usg) in research.

Inclusion Criteria:

All studies:

Voluntary informed consent to participate; healthy, no known renal or urinary tract disease.

Exclusion Criteria:

All studies: not mentioned

Description of Study Protocol:

Recruitment for A, B, C: Respondents to search for subjects

Design:

All 3 studies: Temp and relative humidity measured; Holtain calipers used to measure 7 skinfold sites to calculate BF% using Pollock & Wilmore equation.

A: Survey of fitness and physical training habits, heat exposures 30 d prior to testing; instructed to drink 2-8oz glasses water prior to going to sleep night before and after waking day of testing; no food morning of testing; urine specimen collected in lab as 1^st bladder void, and analyzed for Ucol, Uosm, Usg, Una. Venous blood sample collected and analyzed for Posm, Pna, and Hct. Subjects then consumed 115 mL water and reclined in air-conditioned (22 C) room for 4 hr. Subjects provided a final urine sample for measurement of 4-hr urine volume.

B: Same survey as Study A; same food/water instructions as Study A. Pretest urine sample represented 2nd bladder void of day; this specimen and the final urine specimen (5 min post-exercise) were analyzed for Uosm, Ucol, Usg, and Una. During exercise testing, heart rate and rectal temp constantly monitored. Subjects wore 3 layers of clothing, allowing for only hands and face to be exposed to air. Subjects then entered heated environment chamber (32.4± 0.4 C, 57±19% rh) and stood for 15 min to allow temp and body fluid equilibration. 6mL blood sample taken and analyzed (along with 10-min post-exercise sample) for Posm, Pna, and Hct. Exercise each hour involved 50 min treadmill walking followed by 10 min standing rest. Duration of each trial was scheduled to be 3 hr. Heart rate and rectal temp safety limits: if heart rate exceeded 180 bpm during 5 consecutive min, or if rectal temp exceeded 39 C, exercise was terminated before 3 hour duration, final measurements taken, and subject undressed in 22 C environment; voided to allow postexercise urine volume analysis. During exercise, subjects consumed enough water to wet mouths. Body mass measured on platform scale prior to dressing and after disrobing, to calculate sweat rate (corrected for urine output and water intake).

C: Athletes played 3 strenuous tennis matches (8a, 12p, 4p) on each of the 3 consecutive days in hot, humid conditions. Subjects were able to consume foods and fluids ad libitum during & between matches, and during non-testing hours (6p-8a). Body weight recorded and urine and blood samples collected before and after match play each day. Morning urine specimen represented 2nd void and were analyzed for Usg, Ucol, and Una; blood samples analyzed for Sosm, Pna, and Hct.

Blinding: not mentioned

Intervention: N/A

Stat analyses: A, B, C: calculations of linear regression and Pearson product correlation coefficients between all variables measured. Changes in urine and hematologic measurements during exercise in study B evaluated for significance using Student’s T-test. Study C 2-way MANOVA to assess within-day (pre- and post-exercise), between-day, and F-M differences. Significance level of 0.05; Tukey’s post-hoc test used as necessary.

Data Collection Summary:

Study	Timing of meas	Dependent Variables	Independent Variables	Control Variables
A	At rest; Duration of testing:4.5 hr	Ucol - color scale Usg - refractometer Uosm Pna - selective ion-specific electrodes Posm - osmometer Hct - microhematocrit technique		Temperature - air-conditioned room, 22C
B	Pre- and post-exercise; Duration of testing: 4 hr	Ucol Usg Uosm Pna Posm Hct		Temperature: heated environment, 32.2 ±0.4 C, 57± 19% rh
C	At rest, pre- and post-exercise; Duration of testing: 72 hr	Ucol Usg Uosm Pna Hct Sosm - osmometer		Time of day of exercise: 8a, 12p, 4p

Timing of Measurements

Dependent Variables

Variable 1: brief description (how measured?)
Variable 2: brief description (how measured?)
etc

Independent Variables

Control Variables

Description of Actual Data Sample:

Study	Initial N (Final N)	Age, Ethnicity	Heat Acclimat-ization	Anthro- pometrics	Location Temp (C) Rel Humidity (%)
A	23 M	23±2 yoa,	No	Ht: 179.2±7.5cm Wt: 77.4±12.4kg BF%: 15.3±6.2	Lab, New England, 24±1 36±6
B	11 M	23±2 yoa,	No	Ht: 177.3±6.7cm Wt: 78.6±13.7kg BF%: 11.4±4.7	Lab, New England 32.2±0.4 57±19
C	8 F 12 M	20±2 yoa, Highly-trained college tennis players 21±2 yoa, Highly-trained college tennis players	Yes Yes	Ht: 166.8±10.2cm Wt: 60.3±6.3kg BF%:21.3±4.6 Ht: 180.0±4.9cm Wt: 73.8±8.9kg BF%:8.0±3.0	Field, Florida 27.2-33.7 57-71

Summary of Results:

Study

Variables

Measures

Confidence intervals

Statistical Significance of Group Difference

All 3 studies combined:

Frequency distributitions (pre- and postexercise, F and M)

Ucol

Uosm

Usg

5±2

747±305

1.021±0.008

1-8

137-1357

1.005-1.037

Correlation Coefficients for relationships, all 3 studies combined

Ucol &Usg

Uosm & Usg

Ucol & Uosm

+0.8

+0.97

+0.82

N=54

N=45

N=53

p<0.0001

Study A

Ucol & Usg

Ucol & Uosm

Uosm & Usg

+0.93

+0.92

+0.78

p<0.000001

p<0.0001

p<0.000001

Study B

Pre-exercise:

Uosm & Usg

Usg & Una

Ucol & Usg

Ucol & Uosm

Post-exercise

Ucol & Usg

Ucol & Uosm

Uosm & Usg

+0.98

+0.79

+0.93

+0.92

+0.88

+0.89

+0.96

p<0.000001

p<0.01

p<0.000001

p<0.0001

P<0.0005

p<0.005

p<0.000005

Study C

Pre-exercise, days 1 &4; M, F combined:

Ucol & Usg

Usg & Una

Day 4:

Ucol & Usg

Usg & Una

Sosm & Pna

M-F Differences

Hct, all days

Usg D1, 3

+0.78

+0.42

+0.78

+0.58

+0.53

p<0.0001

p<0.05

p<0.0005

p<0.05

P<0.05

P<0.0001

Other Findings

Author Conclusion:

Ucol may be used in athletic/industrial settings or field studies, where close estimates of Usg or Uosm are acceptable, but should not be used in laboratories where greater precision and accuracy are required.

Uosm and Usg may be used interchangeably to determine hydration status in research settings (lab).

Funding Source:

University/Hospital:

University of Connecticut

Reviewer Comments:

A scale using Urine color (Ucol) as a practical index of hydration may be useful in field settings.

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)	Yes
	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)	Yes
	2.	Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about?	Yes
	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
	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)	Yes
	4.	Is the intervention or procedure feasible? (NA for some epidemiological studies)	Yes

Validity Questions
	1.	Was the research question clearly stated?	Yes
1.	Was the research question clearly stated?		Yes
	1.1.	Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified?	Yes
	1.1.	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
	1.2.	Was (were) the outcome(s) [dependent variable(s)] clearly indicated?	Yes
	1.3.	Were the target population and setting specified?	Yes
	1.3.	Were the target population and setting specified?	Yes
	2.	Was the selection of study subjects/patients free from bias?	???
2.	Was the selection of study subjects/patients free from bias?		???
	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?	???
	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?	???
	2.2.	Were criteria applied equally to all study groups?	???
	2.2.	Were criteria applied equally to all study groups?	???
	2.3.	Were health, demographics, and other characteristics of subjects described?	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?	???
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
	3.	Were study groups comparable?	N/A
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
	3.1.	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?	Yes
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	???
	3.3.	Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.)	???
	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?	Yes
	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?	Yes
	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
	3.5.	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")?	Yes
	3.6.	If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")?	Yes
	4.	Was method of handling withdrawals described?	No
4.	Was method of handling withdrawals described?		No
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	4.1.	Were follow-up methods described and the same for all groups?	N/A
	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%.)	N/A
	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%.)	N/A
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	No
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	No
	4.4.	Were reasons for withdrawals similar across groups?	???
	4.4.	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?	???
	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?	???
5.	Was blinding used to prevent introduction of bias?		???
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	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
	5.2.	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
	5.3.	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
	5.4.	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?	???
	5.5.	In diagnostic study, were test results blinded to patient history and other test results?	???
	6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?	Yes
6.	Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described?		Yes
	6.1.	In RCT or other intervention trial, were protocols described for all regimens studied?	N/A
	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?	Yes
	6.2.	In observational study, were interventions, study settings, and clinicians/provider described?	Yes
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	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?	???
	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
	6.5.	Were co-interventions (e.g., ancillary treatments, other therapies) described?	No
	6.6.	Were extra or unplanned treatments described?	Yes
	6.6.	Were extra or unplanned treatments described?	Yes
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	6.7.	Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups?	Yes
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	Yes
	6.8.	In diagnostic study, were details of test administration and replication sufficient?	Yes
	7.	Were outcomes clearly defined and the measurements valid and reliable?	Yes
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
	7.1.	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
	7.2.	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?	N/A
	7.3.	Was the period of follow-up long enough for important outcome(s) to occur?	N/A
	7.4.	Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures?	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?	???
	7.5.	Was the measurement of effect at an appropriate level of precision?	???
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.6.	Were other factors accounted for (measured) that could affect outcomes?	Yes
	7.7.	Were the measurements conducted consistently across groups?	Yes
	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.	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
	8.1.	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
	8.2.	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
	8.3.	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
	8.4.	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
	8.5.	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?	N/A
	8.6.	Was clinical significance as well as statistical significance reported?	N/A
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	N/A
	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?	N/A
9.	Are conclusions supported by results with biases and limitations taken into consideration?		N/A
	9.1.	Is there a discussion of findings?	Yes
	9.1.	Is there a discussion of findings?	Yes
	9.2.	Are biases and study limitations identified and discussed?	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.	Is bias due to study's funding or sponsorship unlikely?		Yes
	10.1.	Were sources of funding and investigators' affiliations described?	No
	10.1.	Were sources of funding and investigators' affiliations described?	No
	10.2.	Was the study free from apparent conflict of interest?	Yes
	10.2.	Was the study free from apparent conflict of interest?	Yes