| Abstract|| |
Peritonitis is associated with an increasing morbidity and mortality rate in peritoneal dialysis patients. A number of peritonitis cases result in hypoalbuminemia, and in other cases, peritonitis follows a decline in the serum albumin level. However, it is not clear whether the level of serum albumin can be utilized to predict and prevent the incidence of peritonitis. A quasi-systematic search of the literature was conducted in the following databases: Cochrane, EBSCO, ProQuest, AHMED, CINHAL, MEDLINE, and EMBASE, from January 2008 to January 2018. The data was reviewed and extracted from each study. The quality of the studies was assessed using the Critical Appraisal Skills Programme and the Newcastle-Ottawa Scale. Six articles met the stated inclusion criteria of the quasi-systematic review. The study found a significant correlation between a low serum albumin level at the start of continuous ambulatory peritoneal dialysis (CAPD) and the development of peritonitis. Thus, hypoalbuminemia can be utilized as a warning sign of the occurrence of peritonitis in CAPD. Consequently, immediate intervention is required when the level of serum albumin declines in order to prevent peritonitis.
|How to cite this article:|
Alharbi MA. Low serum albumin a predictor sign of the incidence of peritoneal dialysis-associated peritonitis? A quasi-systematic review. Saudi J Kidney Dis Transpl 2020;31:320-34
|How to cite this URL:|
Alharbi MA. Low serum albumin a predictor sign of the incidence of peritoneal dialysis-associated peritonitis? A quasi-systematic review. Saudi J Kidney Dis Transpl [serial online] 2020 [cited 2020 Jul 9];31:320-34. Available from: http://www.sjkdt.org/text.asp?2020/31/2/320/284006
| Introduction|| |
Peritoneal dialysis (PD) is one method of renal replacement therapy (RRT) that has been used as an alternative modality for hemodialysis (HD) for almost four decades. There are two main options with regard to PD modalities: continuous ambulatory peritoneal dialysis (CAPD) and automated peritoneal dialysis (APD). Both modalities require daily dialysis and use the same PD solution. The only difference between them is that the former is manual, involves intermittent exchanges, which are performed 4-5 times daily. In contrast, the latter utilizes a machine to manage both the fluid volume and time of each dialysis cycle and requires fewer connection and disconnection procedures per day compared to the manual modality. Like any other invasive treatment procedure, PD dialysis can lead to various complications ranging from mild to severe.
Peritonitis is the most serious complication of PD and contributes to an increased risk of mortality and morbidity. Indeed, it remains the most significant cause of treatment failure and switching to HD modality. Despite the significant drop in the peritonitis rates, it still accounts for 41.3% of deaths and 20% of technical failures in PD patients., Various factors have been identified as the cause of developing peritonitis,, with a low level of serum albumin being one of the influential factors that require attention because a drop in this precedes the onset of peritonitis. Albumin is a major serum protein that plays a vital physiological function, including the maintenance of colloidal osmotic pressure, the binding of a wide variety of compounds, and the provision of the bulk of plasma antioxidant activity. In PD, a patient’s albumin can also help with fluid removal during the dialysis treatment. To perform these biological roles, the KDOQI (2000) recommended that the serum albumin in dialysis patients be maintained at a level of 40 g/L or above. It is important to note that inflammation and malnutrition both reduce the concentration of albumin by suppressing the synthesis rate,, while inflammation alone is associated with a greater fractional catabolic rate and increased shift of albumin out of the vascular compart- ment. In addition, persistent inflammation is a prominent feature of chronic kidney disease and end-stage renal disease (ESRD), which are caused by multiple factors such as toxic uremic milieu and the dialysis technique itself., Thus, hypoalbuminemia is highly prevalent in ESRD patients.
Indeed, hypoalbuminemia is associated with increase morbidity and mortality rates among dialysis patients., Each 10 g/L decrease in serum albumin has been found to be associated with an increased mortality risk of 47% and 38% in HD and PD, respectively. Additionally, a level of serum albumin less than 38 g/L has been shown to be associated with a significant increase in death among PD patients. Moreover, a decrease in the albumin level below 30 g/L is responsible for a twofold increase in the risk of peritonitis. However, PD can lead to extensive losses of albumin, with up to 4.04 g of protein leakage daily during PD.,
Furthermore, even though a low level of serum albumin is recognized as an inflammatory response and result of poor nutrition, it can increase a patient’s susceptibility to infection alone. Ma et al reported that hypoalbuminemia is a predictor of peritonitis that occurs before commencing PD. Therefore, the serum albumin level can be used as a warning sign preceding the incidence of peritoneal infection. This allows for early initiation of preventive measures and intervention. Since there is no systematic review that explores the correlation between the incidence of peritonitis and a decrease in the level of serum albumin, this study was conducted to systematically review the literature and to summarize the evidence in answer to the following research question: “Is low serum albumin a predictor sign of the incidence of PD-associated peritonitis?”
| Methodology of Literature Search|| |
In order to examine this area further, first, a research question was developed using a Population, Exposure, and Outcome (PEO) model as a structured approach. For this literature search, the PEO was ‘‘Is low serum albumin a predictor sign of PD-associated peritonitis incidence?” From each of the components of the research question a list of keywords was developed, including synonyms with spelling variations, and then used for the literature search [Table 1]. Relevant studies were identified by searching a number of databases, specifically Cochrane, MEDLINE, EMBASE, PubMed, EBSCO, ProQuest and CINHAL in March 2018, using search terms that included “peritonitis” or “PI,” and “peritoneal dialysis” or “PD” and one of the three terms associated with serum albumin (“low serum albumin” or “low serum albumin concentration” or “hypoalbuminemia”). The search was limited to the English language and for research papers published in the period between January 2008 and January 2018. Studies were eligible if they were specifically related to PD patients and included information about serum albumin and peritonitis, as well as being limited to patients above the age of 18 years. In order to provide an unbiased comparison, only studies reporting on PD- associated peritonitis, that is to say, studies that reported data on all peritonitis episodes, regardless of the underlying germs that cause them, were included. Hence, studies reporting on non-dialysis peritonitis and involving children were excluded. Moreover, the research also excluded other confounding factors that cause a low level of serum albumin, such as liver cirrhosis and heart failure. [Table 2] shows the inclusion and exclusion criteria for the search.,,,
| Finding of Literature Search|| |
The search identified 72 potentially relevant studies; however, 33 articles had to be excluded, because they did not include data on peritonitis related to PD. Subsequently, 39 abstracts were screened and 28 articles excluded, since they did not contain a discussion of serum albumin levels. In the next step, 11 full- text articles were selected for detailed analysis, and three articles were additionally identified through the references of the former identified articles. A total of seven articles had to be excluded due to the pre-defined exclusion criteria since they included children as participants and one was in Spanish. Finally, six studies were assessed in terms of their methodological quality and scored as being “acceptable.” The selection process is depicted in [Figure 1], and the characteristics of the studies included in this quasi-systematic review, are shown in [Table 3].,,,,
|Table 3: Characteristics of studies included in the Quasi-systematic review.|
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| Data Quality Assessment|| |
Eligible studies underwent a quality assessment check using the Critical Appraisal Skills Programme to determine the criteria for “adequate quality” following which, the risk of bias was assessed and scored by using the Newcastle-Ottawa Scale (NOS) for the cohort studies, as recommended by the Cochrane Collaboration. The six studies were carried out in two countries in Asia, four in China, and two in Turkey. Although there is a huge difference in culture and health-care systems between the two countries, they are still categorized as the same ethnic group, namely Asian. As a result, the external validity is limited, and as a consequence, the possibility of generalizing and applying the findings to another healthcare system or ethnic group is minimized and requires further research. Moreover, two studies, were conducted by the same team in the same setting, which may increase the risk of bias. However, each study had a different objective; in 2016, the focus of the investigation was on the risk factor of a high peritonitis rate (HPR), and in 2017, factors that influence early-onset peritonitis (EOP) was the subject of the study. The fact that both studies examined if a low level of serum albumin is as a risk factor of peritonitis may support the validity and reliability of the findings and measurement tools.
Indeed, all the articles focused on studying the risk factors of peritonitis, except the study by Ozturk et al which directly explored the decline in serum albumin as a sign of peritonitis. Having low serum albumin as a risk factor and predictor of developing peritonitis in every article, despite the fact they had entirely different sampling and aims, increased the validity of results.
Apparently, all articles using retrospective cohort design as an efficient design for investigating non-therapeutic nephrology research is that they cause less harm and require minimal ethical considerations compared to randomized controlled trials (RCTs)., Moreover, a cohort study is the only observational study that estimates the incidence and analyses predictors that enable relative risk calculations. Unlike any other observational design, a cohort study identifies participants based on their exposure status and follows them through time to measuring the development of the outcome, so it is possible to distinguish whether the exposure preceded or followed the outcome, and thus the cause and effect relationships are clearer. However, they are less likely to indicate causal inferences than RCTs, and there is the potential for error due to confounding factors, as well as being open to selection bias., In view of this, the design selected is considered as a limitation of these studies, and therefore, using a prospective design may be a more rigorous method for exploring this correlation.
In order to minimize both the impact of confounders and the bias in the results, the researchers set up inclusion and exclusion criteria. However, the eligibility criteria did not exclude the confounding factors that influence the incidence of peritonitis or affect the serum albumin level. In addition, none of these articles considered the variation in training, hand hygiene, and nutritional status among the participants, which have been suggested as independent risks in the increase of occurrence of peritonitis., Moreover, all the studies included diabetic mellitus and elderly participants, which are also factors that influence the decline in serum albumin. In the study of Fan et al, the percentage of participants of advanced age was 61.5%. For this reason, their findings demonstrated aging as a risk factor for peritonitis. Indeed, the aging process contributes to a low level of serum albumin in the elderly, as a consequence, the incidence of peritonitis is significantly higher in the elderly. Similarly, participants with diabetic nephropathy have a higher risk of protein loss that leads to a decline in serum albumin and a greater susceptibility to perito- nitis., Thus, including elderly and participants with diabetic nephropathy in those articles, are considered as confounding factors that may affect the findings of those studies since the results might be related to the presence of confounders that influence low albumin level and increase the chance of occurrence of peritonitis. The presence of such confounders seems to weaken the internal validity of the research.
In addition, variation is noticeable in the sample sizes across these articles, as well as the observation period. The studies by Wu et al and Fan et al had more than 1000 participants; whereas, the samples studies by Tian et al, Tian et al, and Keles et al were between 200 and 500 individuals, and reached almost the same findings. However, Ozturk et al had the smallest sample size among these articles, with 51 participants, [Table 3]. None of these studies offered a power calculation, and hence, the author could not decide if the small or large sample size was sufficient for answering the questions posed or were consuming time and resources. Indeed, a sample size estimation should be performed to improve the precision of the final results. Furthermore, a small, clinically significant difference is difficult to identify and may require a larger sample size as compared to a study with a larger clinically significant difference. Irrespective of sample size, conducting these studies in a single center limits the external validity and generalization of the findings. Conducting such studies in multi-centers could rigors the outcome and increasing the validity of findings, considering the risk of bias that may result in a variation in the local protocol, procedure, data collection, and intervention.
Moreover, all the articles collected the data from participants’ medical records over different periods, ranging from 1998 to 2016. During the last two decades there have been evident technical advances in PD therapy, which has caused a significant improvement in patients’ survival and a decrease in the rate of hospitalization. Therefore, this period may be the optimal duration to assess the correlation between peritonitis and serum albumin levels, with minimal to no impact in term of improper technique of PD connection as a confounder, thus increasing the credibility of their results. However, the variation in duration among these studies would not have impacted the results, because the peak development time for peritonitis is 2.5 weeks to four weeks after PD therapy initiation, and a change in serum albumin appears in the blood investigation within 24 h of an occurrence of peritonitis.,
Across all the studies, the ISPD guidelines from 2005 to 2010 were used as the standard to diagnose peritonitis [Table 4] As a consequence, the inter-observer variability was minimized, regardless of the multiple individuals that gathered and entered these data. Having different examiners to measure the exposure and outcomes may have reduced the influence of the researcher in term of the outcomes and decreasing the risk of detection bias.
Indeed, the fact some data was missing in the study by Fan et al increased its risk of bias. Furthermore, losing follow-up of participants in some studies also appears to have resulted in bias to the outcome. In the study by Tian et al around 1.2% of participants were lost to follow-up; Wu et al reported that 87 patients were lost to follow-up, although none of these patients had suffered early peritonitis. Thus, the drop-out did not affect their research findings. Indeed, the studies achieved a follow-up >80%, which is the minimal acceptable follow-up, and hence, there is a limited risk of bias due to the small loss of follow-up in those studies.
In terms of statistics, each study utilized appropriate statistical analysis software, which precisely revealed the findings and inferences, as well as presented them in simple figures and tables. They used Logistic Regression and Cox Proporational Hazard Regression to determine the factors/multivariables associated with peritonitis occurrence, except Ozturk et al, because they were only exploring one variable-low serum albumin and peritonitis - and therefore used the Pearson and Spearman correlation test. Indeed, Cox regression is utilized to consider the impact of a risk factor, in this case, low serum albumin, on the time of the occurrence of an event, which was the development of peritonitis in these studies; whereas, Logistic Regression is used to obtain an odds ratio in the presence of more than one explanatory variable, so that it may minimize the confounding effect by analyzing the association of all the variables together.
The NOS was used to identify the risk of bias in those cohort studies. The six articles that were included in this quasi-systematic review were estimated to be of good quality. [Table 5] demonstrates the risk of bias of these studies, and Appendix 2 shows the NOS for the cohort studies. Indeed, each article had a rating of four stars in terms of selection domain, one star regarding the comparability domain and three stars for the outcome domain. However, even though the researchers attempted to match the exposure and non-exposure group and adjusted the confounders, they could not exclude the risk of bias resulting from the presence of confounders, which may have impacted the outcomes. Even though the risk of bias was similar in these studies, various strengths and limitations were identified during the critical appraisal.
|Table 5: Risk of bias summary using the Newcastle-Ottawa quality assessment tools.|
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| Ethics Considerations|| |
Although, in this research, a quasi-systematic review is used to answer the research question, the author tried to ensure that the included articles had followed the ethical considerations. Overall, five of the studies stated that the research had been approved by a research ethics committee; however, the study by Ozturk et al did not report on ethics consideration. In addition, details relating to confidentiality, the risks that may have resulted from these studies, and informed consent were mentioned, with the exception of the study by Fan et al, which mentioned that written informed consent was obtained from all its participants.
Nevertheless, the ethical considerations of publishing a systematic review have been followed, highlighting concerns about unclear or inappropriate authorship, copying of material from other sources, and dual or duplicate publication.,
| Findings|| |
Overall, all six studies were of good quality and met the inclusion criteria. The total number of patients was 3,853 who were followed- up from 1998 to 2016. In terms of the characteristics of patients, four studies,,, studied CAPD patients only, whereas two articles, included both CAPD and APD, although the percentage of APD included was small.
The average age was 50 ± 14 years in two studies, and 47 ± 15 in three others,, and the median main age in the study of Ozturk et al was 42 years. The study by Fan et al included >60% elderly participants.
Data were extracted and displayed in [Table 5]. Thematic analysis was utilized to conclude the findings from the extracted data. Three major findings emerged from the analysis and are highlighted in [Table 6].
Serum albumin level
Two studies, demonstrated that a serum albumin level was within 35.0 ± 6.4 g/L at the initiation of PD and was associated with the development of peritonitis in EPO group, where peritonitis occurred in the first six months of starting PD therapy, with P = 0.003 and 0.004, respectively. A study by Tian et al reported that the HPR is increased when the serum albumin was 36.2 ± 5.3 g/L (P <0.001), whereas a baseline serum albumin level of 36.4 ± 5.5 g/L was seen to be a predictor of the incidence of PI in the study conducted by Fan et al with P <0.001. Keles et al predicted the development of peritonitis when the level of serum albumin reached 30.5 ± 6.0 with a P <0.001. Ozturk et al found that the serum albumin dropped prior to and one month after an occurrence of peritonitis, however, instead of clarifying the range in serum albumin level associated with the occurrence of peritonitis, they simply reported the mean serum albumin level before and after the occurrence of peritonitis, which was 38.1 g/L (P = 0.026) and 36.5/L (0.025), respectively. [Table 5] shows these findings.
It has become clear that the serum albumin level pre- and post-initiation of PD <40 g/L is associated with a higher incidence of peritonitis. Indeed, these findings are supported by the KDOQI guidelines that requires the serum albumin level to be at a level of 40 g/L or above in dialysis patients. Overall, the articles showed a wide range of serum albumin levels, without no clear indication of whether there is a specific amount present or percentage in decline when peritonitis occurs, and as a result, the author cannot rely on the range of serum albumin level given in these articles.
Regardless of the serum albumin level, in the study by Keles et al, they found that the risk of PI declines with each 10 g/L increase in albumin concentration, with a hazard ratio of 0.39 [confidence interval (CI): 0.24-0.65; P <0.001]. Furthermore, Tian et al and Tian et al found that each 1 g/L rise in serum albumin resulted in decreasing the risk of EPO and HPR by 5%, with an odds ratio of 0.950 [CI: 0.914-0.986; P = 0.007] for the former and, an odds ratio of 0.949 [CI: 0.903-0.998; P = 0.040] for the latter.Therefore, the amount of serum albumin associated with PI is still an issue that requires more investigation.
Low serum albumin and time of peritonitis
It is statistically significant that a decline in serum albumin is a predictor sign of peritonitis. Furthermore, an initial low level of serum albumin is also a greater independent risk factor of PI. However, there is no specific information regarding the clear definition of initial time, whether it is on the 1st day of PD, or the day, weeks, or months preceding the PD therapy.
Low serum albumin prior- peritonitis
Ozturk et al reported that before an occurrence of peritonitis, peritoneal permeability to small solutes increases, and serum albumin decreases, with peritonitis subsequently developing. Consequently, the level of serum albumin drops. Hence, by considering this decline as a warning sign, and immediate intervention can help to prevent an incidence of peritonitis. Five of the studies,,,, demonstrated that a low level of serum albumin before PD commencement is associated with the development of peritonitis, with a P-value of 0.003, <0.001, 0.017 and 0.005, respectively, [Table 5]. In the study by Keles et al, they found that there was a reduction in the serum albumin level before an incidence of peritonitis, regardless of the initial serum albumin value (P <0.001). Thus, a low initial/baseline serum albumin level can be utilized as an indicator of the occurrence of peritonitis.
Low serum albumin post-peritonitis
Only one study reported a decline in serum albumin after a month of peritonitis P = 0.025). Thus, the decreasing level of serum albumin post-peritonitis requires further investigation. Thus, the health-care providers should consider the decline in serum albumin, either before or after peritonitis, and manage the level, so as to prevent recurrent peritonitis and its related morbidity as well as mortality.
Low serum albumin and peritoneal dialysis modality
Four studies,,, reported that low serum albumin is a predictor of occurrence of peritonitis in CAPD patients. Two studies, explored the correlation between a low serum albumin level and peritonitis in both modalities, CAPD and APD. However, they included a small number of participants treated with the APD modality. In addition, both studies did not investigate APD patients separately; they included them with CAPD patients in the same group. For this reason, the correlation between peritonitis in the patients being treated with the APD modality and their level of serum albumin requires further research. Hence, it seems that a low level of serum albumin can be regarded as a warning sign for. the occurrence of peritonitis in CAPD patients.
| Discussion|| |
The findings of the present quasi-systematic review demonstrate that a low serum albumin level before starting PD therapy is associated with an increased risk in subsequently developing peritonitis. Moreover, the level of serum albumin seems to drop prior to an episode of peritonitis, even if the initial serum albumin begins within a normal level. Thus, a low serum albumin is considered as a predictor sign of the occurrence of peritonitis in CAPD. Furthermore, the risk of peritonitis is significantly decreased when the serum albumin level is >40 g/L. Although all the studies found an inverse correlation between a low serum albumin level with peritonitis occurrence, the range of serum albumin level associated with peritonitis varied across these studies, and therefore no clear conclusion about the albumin range and incidence of peritonitis can be drawn. Moreover, further studies are required to examine the relationship between the serum albumin level and the development of peritonitis.
In view of this, the findings of these studies suggest that health-care providers need to consider the serum albumin level when monitoring CAPD patients, not only as a nutritional marker but also an indicator of peritonitis. A low level of serum albumin prior to the initiation of PD needs to be managed before CAPD commencement. Additionally, a long- term action plan is required to maintain the level within or above the lowest limit of a normal range of serum albumin, which is 40 g/L, so as to minimize the risk of an incidence of PI and its consequent complications. Thus, any decrease in the albumin concentration requires attention and immediate action.
Several studies have associated decreased serum albumin levels with increased mortality and morbidity in dialysis patients., A study by Mehrotra et al reported that the risk of cardiovascular and infection-related mortality is increased when there is a low level of serum albumin in both PD and HD patients. They found that the patients with an initial serum albumin level of <30 g/L had a three-fold increase in risk of cardiovascular mortality and 3.4-fold higher risk of death due to infection. However, none of these studies assessed the impact of low serum albumin level on developing peritonitis.
In addition, the findings of this quasi-systematic review seem to support the assertions of a number of authors regarding the care of patients receiving PD, who have suggested that hypoalbuminemia is a risk factor for PI. Narrative reviews by Cho and Johnson and Kerschbaum et al, classified hypoalbumi- nemia as a modifiable risk factor for PD peritonitis that can be managed and prevented. Moreover, in a retrospective cohort study by Sirivongs et al, which was conducted in Thailand, it was found that hypoalbuminemia is a risk factor for developing the first episode of peritonitis in CAPD patients.
The findings of this quasi-systematic review agree with the literature in this area. A retrospective study analysis of 393 PD patients in the United States by Wang et al reported an initial serum level <29 g/L was associated with an approximately two-fold greater risk for developing peritonitis. In addition, a similar study by Chow et al demonstrated that an increase in the baseline serum albumin level 10 g/L was associated with a 67% decrease in the risk of developing peritonitis.
Furthermore, low levels of serum albumin have also been reported to be predictors of pre- training peritonitis (PTP). Ma et al found that the level of serum albumin was the only independent predictor of peritonitis and mortality among PD patients during training and before exposure to the PD fluid. In addition, it also decreased the probability of the patient’s survival. They reported that every 10 g/L increase in serum albumin concentration was associated with 11% lower odds of PTP, with an odds ratio of 0.89 (CI: 0.82-0.97; P <0.01). However, their study consisted of small sample size and explored the peritonitis incidence before training and starting dialysis.
This study is the first quasi-systematic review to date that explored the serum albumin level as a predictor and warning sign of the incidence of peritonitis in CAPD. However, there are several limitations of this study. First, it included single-center retrospective studies and only investigated CAPD patients, so the findings cannot be extrapolated to the APD modality. Second, although the studies identified a correlation between low serum albumin levels and the occurrence of peritonitis, the impact of confounders on findings cannot be ignored. In view of this, additional studies are required to consider confounding factors, namely variation in nutritional status, training, age, and hand hygiene, as well as an exploration of the correlation between serum albumin levels and the risk of peritonitis in APD. Moreover, the effect of early intervention in managing serum albumin and preventing the occurrence of PI also needs further research.
| Conclusion|| |
This is the first quasi-systematic review conducted to investigate the possibility of utilizing serum albumin as a marker to predict the incidence of peritonitis. Interestingly, even though the level of serum albumin is known as a nutritional indicator in dialysis patients, it is not widely known that it can be used to monitor the likelihood of developing peritonitis in CAPD patients. Hypoalbuminemia should be managed prior to the initiation of PD therapy to reduce the risk of develompment of peritonitis. Thus, care providers at PD centres could prevent peritonitis by closely observing the serum albumin level, and then addressing and immediately treating any decline in its concentration, therefore reducing the peritonitis rate and its potential complications.
Conflict of interest: None declared.
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Muneera Aiad Alharbi
Department of Critical Care Nursing, College of Nursing, Qassim University, P. O. Box 40286, Buraydah 51452
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6]