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Influence of uvulopalatopharyngoplasty on serum uric acid level in obstructive sleep apnea patients

  • Yu-long Zheng EMAIL logo , Yu-feng Wan , Cheng-lan Xie , De Huai , Yi Wang , Yuan-qiang He , Chuan-qin Xu , Jian-hui Chen and Dong-hui Zheng EMAIL logo
Published/Copyright: April 28, 2016
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LaboratoriumsMedizin
From the journal LaboratoriumsMedizin Volume 40 Issue 3

Abstract

Background: The objective of this study was to determine whether there is an association between successful uvulopalatopharyngoplasty (UPPP) and serum uric acid in patients with obstructive sleep apnea (OSA), and identify the risk markers for successful UPPP in OSA patients.

Methods: We performed a prospective cohort study of 73 adult patients with OSA who underwent surgery (nasal or UPPP) at a major, urban, academic hospital in Huaian from 2011 to 2014 who had preoperative and postoperative clinical and laboratory profiles. Demographic, clinical, laboratory, and PSG parameters were carefully recorded. Logistic regression was used for the multivariate analysis of independent risk factors.

Results: Changes of uric acid (UA), changes of C-reactive protein (CRP), changes of triglyceride, changes of high density lipoprotein before and after UPPP were significantly higher in OSA patients with successful UPPP than in those with unsuccessful UPPP (p<0.05). Among these patients, multiple logistic analyses indicated the independent risk factors for successful UPPP in the OSA subjects included changes of UA and CRP before and after UPPP. The diagnosis analysis showed that changes of UA and CRP before and after UPPP had a significant ability to reflect UPPP success in the OSA patients.

Conclusions: The novel finding of this study is that the successful UPPP in OSA patients is strongly related to changes of serum UA level, CRP before and after operation. These results might be helpful for providing valuable information to reflect the effect of UPPP operation, regardless of UA and CRP before operation.

Keywords: C-reactive protein; obstructive sleep apnea; uric acid; uvulopalatopharyngoplasty

Introduction

Obstructive sleep apnea (OSA) is one of the common chronic respiratory conditions, affecting 2% of women and 4% of men worldwide, which causes significant morbidity and mortality [1–3]. Individuals who meet the following criteria are confirmed for clinical OSA: at least five episodes of apnea or hypopnea per hour of sleep with PSG test [apnea-hypopnea index (AHI) ≥5] and excessive daytime sleepiness. Treatment of OSA patients with nasal continuous positive airway pressure (CPAP), a method of pushing air through the airway, has shown significant improvements in objective and subjective sleepiness, quality of life and cognitive function [4, 5]. However, the major barrier to achieving clinically effective treatment is non-compliance with CPAP therapy. Due to low adherence to CPAP between 17% and 54% [6], a large group of patients do not get adequate therapy. Accordingly, physicians may recommend other options for their patients with OSA, including risk factor modification such as weight loss, oral appliances that advance the mandible or tongue during sleep [7], or various surgical procedures to bypass or expand the upper airway [8].

Since it was introduced in 1981, uvulopalatopharyngoplasty (UPPP) has been one of the most common surgical procedures to relieve airway obstruction. It mainly involves tonsillectomy (if not performed previously), trimming and reorientation of the posterior and anterior tonsillar pillars, and excision of the uvula and posterior palate [9]. UPPP is often combined with other nasopharyngeal or oropharyngeal procedures. The reported success of UPPP as a treatment of OSA is between 16% and 83%, depending on the definition of a positive outcome [9]. Some authors have defined surgical success or cure after UPPP as a 50% reduction in the AHI, whereas others combine this criterion with an absolute AHI of 20 or less [10, 11].

Regardless of the debate whether it is a predictor or a causative factor, uric acid (UA) has been clearly associated with oxidative stress and inflammation in several pathological conditions [12]. Serum uric acid (UA) has been associated with a pro-inflammatory state in human subjects and particularly with an increase in inflammatory markers. Serum UA levels are also reported to be useful markers of cardiovascular morbidity and mortality risk [13].

Although numerous clinical studies regarding UPPP in OSA patients have been published, there are few data addressing the association between uric acid levels and UPPP success rate in OSA patients. In this study, we aimed to investigate if the serum uric acid level is an independent predictor of UPPP success in OSA patients, or as other risk factors in a prospective cohort of OSA patients.

Patients and methods

A prospective, observational cohort study was carried out. Written informed consent was obtained from all of the legal guardians. The study was approved by the Ethics Committee of the hospital, in accordance with the Declaration of Helsinki.

Study population

This study was performed in the department of ENT and Respirology of the Affiliated Huai’an Hospital of Xuzhou Medical College in Huai’an, P.R. China. All patients with OSAS were also diagnosed with PSG. Before enrollment, all subjects were asked about their regular medications and medical history.

In this cross-sectional study we recruited consecutive OSA patients in our hospital between January 2011 and December 2014. A total of 106 patients were finally studied (Figure 1). Exclusion criteria were thyroid dysfunction (including subclinical hyperthyroidism), history of coronary artery disease, valvular heart disease, congestive heart failure, previous cardiac surgery, myocardial infarction, hypertrophic and dilated cardiomyopathy and history of a disabling cerebral infarction or transient ischemic attack (TIA), recent infection, autoimmune or inflammatory diseases, respiratory diseases and administration of drugs that affect UA metabolism (apart from diuretics), and consumption of alcoholic beverages.

Figure 1: Flow chart showing the distribution of the patients eligible for inclusion in the study.
Figure 1:

Flow chart showing the distribution of the patients eligible for inclusion in the study.

Blood collection and biochemical analysis

Laboratory examinations, including complete blood count and biochemical investigations, were performed in the fasting state. Levels of total cholesterol, triglycerides, HDL-C, and LDL-C were measured by enzymatic colorimetric methods using an Olympus AU 2700 autoanalyzer (Olympus, Tokyo, Japan). The white blood cell (WBC) count was determined using a Coulter counter (Mindray BC-5500, Shenzhen, China). The levels of serum C-reactive protein (CRP) was assayed with the immunonephelometric method (Dade Behring Marburg, Marburg, Germany). The reference concentrations for CRP were 3 mg/L. As a measure of renal function, the baseline glomerular filtration was estimated (eGFR) using the abbreviated Modification of Diet in Renal Disease (MDRD) Study equation [14]: eGFR (mL/min/1.73 m2 of body surface area)=186× (serum creatinine in mg/dL)−1.154×(age in years)−0.203×0.742 in female subjects. Serum uric acid levels were measured by standard uricase enzymatic test using an Olympus AU 2700 autoanalyzer (Olympus, Tokyo, Japan) (normal range of uric acid levels: 150–440 μmol/L for men, 90–380 μmol/L for women).

Uvulopalatopharyngoplasty for OSA

All surgeries were performed under general anesthesia. All patients underwent preoperative CT imaging and upper airway endoscopy to find the obstructive area in the upper airway, which guided the indicated procedure. According to the different types of obstruction and operation, the patients were divided into two groups: OSA patients with nasal obstruction and relevant anatomic abnormalities were treated with nasal surgery (septoplasty with turbinate reduction±endoscopic sinus surgery, n=23). OSA patients with oropharyngeal obstruction were treated with palatal surgery (UPPP with tonsillectomy, n=59). All patients met standard surgical criteria. For the nasal surgery, we performed surgical inferior turbinate reduction and standard septoplasty, and, if indicated, nasal polypectomy and functional endoscopic sinus surgery according to the patient’s particular condition. For the palatal surgery, we excised of the tonsils and posterior soft palate, and trimmed the uvula, with suture closure of the tonsillar pillars. All nasal surgery and palatal surgery was performed using standard techniques by three attending surgeons fully-licensed to practice surgery in China.

A successful operation is defined as reduction of AHI more than 50% from baseline. An unsuccessful operation is defined as reduction in AHI of <50% from baseline. Patients who worsened are defined as increase in AHI more than 10% from baseline.

Outcomes and follow-up

At 6 months postoperatively, patients were asked to return to the hospital for blood draw for repeat blood count and biochemical testing and PSG test. At that visit, we repeated the baseline evaluation, including: sleepiness scale, PSG, complete blood count, biochemical investigations, serum CRP and uric acid level. Because all patients had been encouraged to lose weight and to adopt a healthier lifestyle, focusing on physical exercise and a improved diet, those presenting with changes in the BMI (>5% from baseline), significant alterations in physical activity, dietary or alcohol habits, along with those with a newly diagnosed disease or use of uric acid-lowering medications were excluded from the study. Blood samples were obtained following an overnight PSG between 8:00 and 9:00 am.

Polysomnography

Polysomnography was started at 9 pm and ended at 6:30 am. All subjects underwent an attended overnight sleep study with the use of the Jaeger Sleeplab 1000 (Jaeger, Würzburg, Germany) polysomnography system. The following signals were included: EEG; electroocculogram; submental electromyogram; and anterior tibialis electromyogram. Additionally, ECG and heart rate were recorded simultaneously. Snoring was recorded by a microphone placed at the jugular vein, and air flow was recorded by combined oronasal thermistors, while arterial oxyhemoglobin saturation was recorded by a finger pulse oximeter. Thoracic cage and abdominal motion were recorded by inductive plethysmography. EEG recordings were manually scored according to standard criteria.

Apnea was defined as the cessation of airflow at the nose and mouth lasting for ≥10 s. Hypopnea was defined as a decrease of ≥30% in thoracoabdominal motion associated with a fall in the baseline oxygen saturation of ≥4%. All AHI values were calculated to express the number of episodes of apnea and hypopnea per hour of total sleep time.

Statistical analysis

Continuous data are presented as mean±standard deviation. Univariate analysis to assess the predictive value of clinical variables on UPPP success was computed using the unpaired independent samples T-test for continuous variables and the χ2-test and Fisher’s exact test if necessary for categorical variables. A p-value <0.05 was considered statistically significant. To test the independence of the risk factors for UPPP success in OSA patients, the significant variables (p<0.05) in the univariate analyses were entered into a multivariate logistic regression model with backward selection of independent variables. Risk factors were checked for confounding and co-linearity. All analyses were performed with the SPSS software version 16.0 (SPSS Inc., Chicago, IL, USA).

Results

Clinical characteristics

Clinical and instrumental characteristics of the study population were expressed in Table 1. Seventy-three consecutive OSA patients with UPPP surgery were enrolled in this study. The screened population consisted of 18 patients with nasal surgery, and 55 patients with palatal surgery. The average age of the patients was 54.8±15.0 years, and 79.5% of the 73 patients were male. Table 1 shows the comparative analysis of the studied characteristics according to nasal surgery and palatal surgery in OSA patients. There were no significant differences between the two groups with respect to age, gender, body mass index, neck circumference, waist circumference, hip circumference, eGFR, WBC count, CRP, uric acid, TG, TC, HDL and LDL. No difference was observed between the two groups in PSG test (Apnea hypopnea index, lowest SaO2, percentage of time with SaO2<90% and Epworth sleepiness scale). The prevalences of diabetes, hypertension were similar in the OSA patients with nasal surgery and palatal surgery. There were also no statistical differences between the two groups in terms of the medical drug therapies such as statins, diuretics, angiotensin converting enzyme (ACE) inhibitors or angiotensin II receptor blockers (ARBs), β-blockers, and calcium channel blockers.

Table 1:

Baseline characteristics and follow-up of the study population.

Characteristics (n=73)BaselineFollow-up
Nasal surgery (n=18)Palatal surgery (n=55)p-ValueNasal surgery (n=18)Palatal surgery (n=55)p-Value
Age, years59.0±15.653.5±14.70.06––
Male/female14/442/110.90––
BMI, kg/m227.05±4.0927.59±2.810.8726.9±4.6627.33±3.740.72
Neck circumference, cm33.8±2.534.0±2.50.06––
Waist circumference, cm96.0±8.897.4±9.90.25––
Hip circumference, cm99.9±9.4103.1±8.90.55–
Waist/hip ratio0.97±0.10.95±0.10.58––
Diabetes6(10.9%)1(5.6%)0.51––
Hypertension6(10.9%)2(11.1%)0.38––
Laboratory examinations
 Uric acid (μmol/L)465.3±131.9429.0±120.50.32308.1±66.2323.3±91.60.52
 Triglyceride, mg/dL2.16±1.321.90±1.300.941.08±0.661.63±1.110.06
 Total cholesterol, mg/dL4.90±1.234.55±1.080.284.57±1.114.50±0.920.81
 HDL, mg/dL1.26±0.521.24±0.370.741.49±0.261.30±0.290.02
 LDL, mg/dL2.78±4.092.55±0.740.212.57±0.842.45±0.610.54
 eGFR, mL·min−1·m−2107.7±36.895.6±29.60.75101.8±27.2112.1±43.90.36
 WBC (10*9/L)6.80±2.437.25±2.520.156.59±2.036.91±1.840.53
 C reactive protein, mg/L7.11±2.377.40±2.850.474.10±1.924.51±2.140.47
Drug therapy
 Statins1(1.8%)1(5.6%)0.40––
 ACEI/ARBs2(3.6%)1(5.6%)0.72––
 Beta-blockers4(7.3%)3(16.7%)0.08––
 CCBs1(1.8%)3(16.7%)0.24––
Polysomnography
 AHI, events/h46.50±12.3342.87±12.750.1517.89±6.3020.35±8.540.27
 Lowest SaO2, %68.33±12.5372.25±11.400.6183.28±3.0881.75±4.340.17
 SaO2<90% (%TST)32.16±11.5932.89±9.270.555.56±2.396.20±3.110.43
 Epworth sleepiness scale15.72±2.7416.44±3.680.8613.50±2.4812.95±2.970.48
 Successful surgery––13(72.2%)38(69.1%)0.80

BMI, body mass index; HDL, high density lipoprotein; LDL, low density lipoprotein; WBC, white blood cell count; eGFR, estimated glomerular filtration rate; ACEI, angiotensin-converting enzyme inhibitors; ARB, angiotensin receptor blocking agents; CCB, calcium channel blockers; AHI, apnea hypopnea index; SaO2<90% (%TST), percentage of time with SaO2<90%.

Change of biochemical parameters and PSG pre- and post-surgery

We first examined the entire group of subjects (n=73). Serum uric acid, C reactive protein and triglyceride decreased after surgery (p<0.01, respectively). PSG showed that AHI, lowest SaO2, SaO2<90% (%TST) and ESS significantly decreased after surgery (Table 1). There were no significant changes in serum HDL, LDL, TC and WBC (p>0.05, all).

Subgroup analysis

We next divided the subjects according to the type of surgery. For patients who underwent palatal surgery (n=55), the level of serum uric acid and CRP significantly decreased (p<0.001, all), and the AHI, lowest SaO2, SaO2<90% (%TST), ESS significantly improved after surgery (p<0.001, all) in the PSG test. However, the serum TG, HDL, LDL and TC showed no significant changes after surgery (p>0.05, all). For those who had nasal surgery (n=18), only the level of serum uric acid, CRP and triglyceride significantly decreased after surgery (p=0.001, 0.003, 0.002, respectively), and the AHI, lowest SaO2, SaO2<90% (%TST), ESS significantly improved after surgery in the PSG test (p<0.001, all) (Table 1).

The subjects were divided into the successful UPPP and unsuccessful UPPP group according to PSG test. In successful group (patients with successful UPPP), the serum uric acid, CRP, TG, and HDL decreased (p<0.001, <0.001, =0.03, 0.03, respectively), and the AHI, lowest SaO2, SaO2<90% (%TST), ESS significantly improved (p<0.001, all) in the PSG test. In unsuccessful group (patients with unsuccessful UPPP), only the AHI, Lowest SaO2, SaO2<90% (%TST), ESS significantly improved (p<0.001, <0.001, <0.001, =0.01, respectively). The changes of serum lipid parameters and PSG test are listed in Table 2.

Table 2:

Comparative univariate analysis of successful or unsuccessful UPPP according to the characteristics of the patients of the study cohort.

VariablesAll cases (n=73)Successful UPPP (n=51)Unsuccessful UPPP (n=22)
BaselineFollow upp-ValueBaselineFollow upp-ValueBaselineFollow upp-Value
BMI, kg/m227.5±3.227.2±3.90.7327.6±3.327.2±4.00.6327.1±2.727.3±3.90.84
Uric acid, μmol/L437.9±122.6319.6±85.3<0.001471.1±112.3315.4±80.2<0.001360.9±110.2329.2±95.30.23
Triglyceride, mg/dL1.97±1.301.50±1.050.0012.24±1.361.24±0.730.031.80±1.071.38±0.940.19
TC, mg/dL4.64±1.124.52±0.960.494.48±1.114.55±1.000.755.00±1.094.45±0.890.08
HDL, mg/dL1.24±0.411.35±0.290.081.16±0.351.32±0.300.031.44±0.471.41±0.270.83
LDL, mg/dL2.61±0.812.48±0.670.322.54±0.812.46±0.670.622.78±0.792.53±0.670.32
eGFR, mL·min−1·m−2104.7±35.3109.5±40.50.43103.6±31.3109.9±40.90.39107.4±44.0108.8±40.70.91
WBC count (10*9/L)7.13±2.496.83±1.880.417.22±2.606.78±1.920.336.94±2.226.95±1.830.98
CRP, mg/L7.33±2.724.41±2.09<0.0018.06±2.673.99±1.86<0.0016.03±2.535.07±2.400.23
AHI, events/h42.7±12.920.8±9.8<0.00144.8±13.018.6±8.3<0.00137.3±11.425.4±10.4<0.001
Lowest SaO2, %71.3±11.782.1±4.1<0.00170.4±11.382.9±3.9<0.00173.3±12.780.4±4.1<0.001
SaO2<90% (%TST)32.7±9.86.0±2.9<0.00134.0±9.65.6±3.00.00129.7±9.97.1±2.6<0.001
ESS16.3±3.4713.1±2.85<0.00116.4±3.712.8±2.8<0.00116.0±3.013.6±3.00.01

BMI, body mass index; eGFR, estimated glomerular filtration rate; TC, total cholesterol; HDL, high density lipoprotein; LDL, low density lipoprotein; WBC, white blood cell; CRP, C reactive protein; AHI, apnea hypopnea index; SaO2<90% (%TST), percentage of time with SaO2<90%; ESS, Epworth sleepiness scale.

Factors that were associated with successful UPPP in OSA patients were shown in Table 2. In multivariate regression analysis, the best independent risk factors for successful UPPP included changes of serum uric acid level [OR(odds ratio) 0.991; 95% CI, 0.985–0.997; p=0.005], and changes of serum CRP (OR 0.765; 95% CI, 0.609–0.960; p=0.021) before and after operation (shown in Table 3).

Table 3:

Independent risk factors for successful UPPP (multivariate logistic regression analysis).

VariablesWaldOR (95% CI)p-Value
Deta uric acid7.8950.991(0.985–0.997)0.005
Deta C reactive protein5.3540.765(0.609–0.960)0.021
Deta triglyceride0.0450.955(0.626–1.457)0.832
Deta high density lipoprotein0.1591.326(0.332–5.296)0.690

Deta uric acid, deta C reactive protein, deta triglyceride, deta high density lipoprotein, the variation of uric acid, C reactive protein, triglyceride and high density lipoprotein before the UPPP and follow up.

ROC analyses

The ROC curve for changes of uric acid and CRP for successful UPPP comparison was shown in Figure 1. Accordingly, the AUCs were calculated for evaluation and compared. In the patients with successful UPPP, the changes of serum uric acid and CRP showed significant differences (all p<0.05) (shown in Figure 2).

Figure 2: Comparison of the ROC plots of different parameters with respect to their ability to reflect significant differences in the AUCs for successful UPPP.
Figure 2:

Comparison of the ROC plots of different parameters with respect to their ability to reflect significant differences in the AUCs for successful UPPP.

Discussion

In the present study, we have shown that the changes of serum UA levels before operation and follow-up in 6 months for OSA patients were an independent predictor of successful UPPP. Additionally, the great changes of serum CRP were observed in OSA patients with successful UPPP. To date, most studies have focused on changes of pre- and post-surgery AHI to determine the effects of the operation. Our results support a role for non-traditional outcome measures in assessing the beneficial effect of surgery in OSA. This is the first study to our knowledge that has assessed serum UA, a widely available and rapidly measured biomarker, as a predictor of successful UPPP in a prospective cohort of OSA patients.

Uvulopalatopharyngoplasty is the most common surgical procedure performed for the treatment of OSA, but the success rate and the role of UPPP in the management of OSA are not fully elucidated because most studies are limited by small sample size, lack of consensus on a clear definition of surgical success, and an inability to compare UPPP in a blinded manner with CPAP. Traditionally, a successful outcome of UPPP has been defined as achieving a reduction in AHI of at least 50% and/or a residual AHI of 20 or less. Many studies suggest that successful UPPP is associated with an improvement in clinical results including disease-specific quality of life, cardiovascular outcomes, and a reduction in automobile accidents [15–17]. In addition, a recent study reported that isolated UPPP significantly improves subjective sleep apnea symptoms in patients with OSA regardless of postoperative objective results [18].

A large body of evidence has identified OSA as an independent risk factor for cardiovascular morbidity and mortality with multiple associated mechanisms [19]. One of them is the oxidative stress [20], which is also a common pathway linked to uric acid production. Uric acid is the end point of the metabolism of purine compounds, produced in the liver from the degradation of dietary and endogenously synthesized purine compounds via the xanthine oxidase reaction, which irreversibly oxidizes xanthase to uric acid [21]. During the production of uric acid, ROS are generated as byproduct and have an important role in the increased vascular oxidative stress. Importantly, xanthine oxidase mediates intermittent hypoxia-induced vascular dysfunction and administration of allopurinol can prevent it by increasing intermediates, hypoxanthine and xanthine, and decreasing the final product uric acid [22]. In fact, oxidative stress is reflected by uric acid levels, and its concentration decreases after treatment of sleep disordered breathing according to improvement of the respiratory disturbance index and oxygen desaturation index [23]. In this study, the AHI, lowest SaO2 and SaO2<90% (%TST) significantly improved in the patients with successful UPPP, and changes of uric acid level decreased dramatically in those patients. Impact of UPPP on uric acid level can be explained above. Elevated serum uric acid levels are also associated with increased risk for the ocurrence of cardiovascular events [24].

Although CRP is a nonspecific marker of inflammation, recent studies have shown that C-reactive protein, circulating markers associated with cardiovascular morbidity have been found to be elevated in patients with OSA [25]. Epidemiological studies have shown that CRP levels are a strong independent predictor of risk and an active pathogenic agent of future myocardial infarction, stroke, peripheral arterial disease, and vascular death among persons without known cardiovascular disease [26]. Possible mechanisms of cardiovascular dysfunction with increased levels of CRP have been described recently. CRP is found within atheromatous plaque, correlates with vascular dysfunction, and promotes the secretion of inflammatory mediators by vascular endothelium [27–29]. CRP itself induces adhesion molecules and the production of monocyte chemoattractant protein-1 in human endothelial cells and sensitizes endothelial cells to the cytotoxic process by CD4+T cells [30, 31]. A recent meta-analysis has shown that patients with OSAS had a statistically significant higher level of CRP and this effect was positively influenced by OSAS severity [32]. These findings are in line with the results of our study, in which the multivariate analysis on the successful identification of UPPP in the OSA patients showed that patients who had higher differences of CRP before and after UPPP were more likely to acquire successful operation.

Dyslipidemia caused by OSA can increase the morbidity and mortality of cardiovascular and metabolic diseases. Although the precise mechanisms are unknown, animal studies found that intermittent hypoxia causes increases in TC, HDL, TG, and LDL [33]. Some researchers found that intermittent hypoxia may disrupt lipid metabolism by increasing adipose tissue lipolysis and FFA flux to the liver, up-regulating hepatic triglyceride biosynthesis and lipoprotein secretion, and suppressing lipoprotein clearance [34, 35]. In our study, we found a small but significant decrease in triglyceride, but no significant improvement in LDL, TC, or HDL. We also found that the successful UPPP group had a better improvement on lipid profiles than unsuccessful surgery, especially for TG. We speculate that different lipid parameters are more or less sensitive to intermittent hypoxia, though we cannot exclude inadequate power as a reason for these differences.

It can be concluded that the present article is the first study in adults methodologically designed to determine whether serum uric acid is a good predictor of UPPP in OSA patients. Based on the results obtained in this study, monitoring the appropriate parametres forms a crucial part of the management of OSA patients and certainly affects the postoperative prognosis of UPPP.

Limitations

The present study had several limitations. First, the monocenter nature of the study and the relatively small sample size are the main limitations. Second, specific inflammatory and oxidative stress markers were not assessed. Therefore, the results should be confirmed in prospective cohort studies. Third, in the present study, this result may be confounding and would have resulted in attenuated risk estimates because we could not eliminate the selection bias.

Author contributions: Study design, data collection, statistical analysis, data interpretation, manuscript preparation, literature search, funds collection: Yu-long Zheng, Yu-feng. Wan; Study design, manuscript preparation, literature search: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission.

Research funding: None declared.

Employment or leadership: None declared.

Honorarium: None declared.

Competing interests: The funding organization(s) played no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the report for publication.

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Received: 2015-11-30
Accepted: 2016-3-15
Published Online: 2016-4-28
Published in Print: 2016-6-1

©2016 by De Gruyter

This article is distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

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  2. Labormanagement/Laboratory Management / Redaktion: E. Wieland
  3. Der Einfluss der DIN EN ISO 15189 auf die Ergebnissicherheit in der Virusdiagnostik
  4. Entzündung und Sepsis/Inflammation and Sepsis / Redaktion: P. Fraunberger
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  6. Infektiologie und Mikrobiologie (Schwerpunkt Bakteriologie)/Infectiology and Microbiology (Focus Bacteriology) / Redaktion: P. Ahmad-Nejad/B. Ghebremedhin
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  11. Opinion Paper
  12. Equivalence limits of reference intervals for partitioning of population data. Relevant differences of reference limits
  13. Originalartikel/Original Articles
  14. Influence of uvulopalatopharyngoplasty on serum uric acid level in obstructive sleep apnea patients
  15. Correlation between severity of migraine attacks and IgE level in peripheral blood
  16. Kurzmitteilung/Short Communication
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https://doi.org/10.1515/labmed-2015-0110
Keywords for this article
C-reactive protein; obstructive sleep apnea; uric acid; uvulopalatopharyngoplasty
Creative Commons
BY-NC-ND 3.0

Articles in the same Issue

  1. Frontmatter
  2. Labormanagement/Laboratory Management / Redaktion: E. Wieland
  3. Der Einfluss der DIN EN ISO 15189 auf die Ergebnissicherheit in der Virusdiagnostik
  4. Entzündung und Sepsis/Inflammation and Sepsis / Redaktion: P. Fraunberger
  5. HMGB1, nucleosomes and sRAGE as new prognostic serum markers after multiple trauma
  6. Infektiologie und Mikrobiologie (Schwerpunkt Bakteriologie)/Infectiology and Microbiology (Focus Bacteriology) / Redaktion: P. Ahmad-Nejad/B. Ghebremedhin
  7. Improvement in detecting bacterial infection in lower respiratory tract infections using the Intensive Care Infection Score (ICIS)
  8. Evaluation of the compatibility of Phoenix 100 and Microflex LT MALDI-TOF MS systems in the identification of routinely isolated microorganisms in the clinic microbiology laboratory
  9. Mini Review
  10. Liquorzytologie: Eine aussagekräftige Methode zur Diagnostik von Erkrankungen des Zentralnervensystems
  11. Opinion Paper
  12. Equivalence limits of reference intervals for partitioning of population data. Relevant differences of reference limits
  13. Originalartikel/Original Articles
  14. Influence of uvulopalatopharyngoplasty on serum uric acid level in obstructive sleep apnea patients
  15. Correlation between severity of migraine attacks and IgE level in peripheral blood
  16. Kurzmitteilung/Short Communication
  17. Comparison of the novel Maglumi ferritin immunoluminometric assay with Beckman Coulter DxI 800 ferritin
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