Bariatrik cerrahi uygulanan hastalarımızda preoperatif RDW yüzdesinin kilo kaybı tahmini ile olan ilişkisinin retrospektif incelenmesi
The impact of the preoperative red blood cell distributionwidth value on weight loss estimation after bariatricsurgery: A retrospective study
Yazar: KAMİL ERÖZKAN
Danışman: PROF. DR. ÖZGÜR FIRAT
Ege Üniversitesi / Tıp Fakültesi / Genel Cerrahi Ana Bilim Dalı
Derece: Tıpta Uzmanlık, 2019
Konu: Genel Cerrahi = General Surgery

Özet:
Giriş: Morbid obezite tüm dünyada yaygın bir sağlık sorunu olarak karşımıza çıkmaktadır. Çağımızda, sosyokültürel hayatı engelleyip, mortalite ve morbiditeyi arttıran, bireylerin yaşam kalitesini düşüren önemli bir problemdir. Diyet, egzersiz ve medikal tedavi ile kalıcı başarılı sonuçlar alınamamıştır. Bu nedenle obezite cerrahisi gündeme gelmiştir. Fakat hangi hastanın bu cerrahiden fayda sağlayacağı açık değildir. Bununla ilgili net bir prediktif değer henüz ortaya konmamıştır. Biz de çalışmamızda eritrosit dağılım hacminin (RDW) kilo kaybı üzerine prediktif bir değer olup olmadığını değerlendirdik.
Metot: Çalışma öncesinde etik kurul onayı alınmış olup, Haziran 2011 – Haziran 2019 tarihleri arasında Ege Üniversitesi Genel Cerrahi Anabilim Dalı'nda morbid obezite nedeniyle bariatrik cerrahi uygulanan hastalar retrospektif olarak ele alındı. Daha önce başka bir bariatrik cerrahi prosedür uygulanıp revizyon uygulanan hastalar ile intragastrik balon uygulaması yapılan hastalar çalışma dışı bırakıldı. Yaş, cinsiyet, komorbidite durumu, preoperatif ve kontrollerdeki vücut kitle indeksi (VKİ), operasyon türü, ve tekrar kilo alımı değerlendirildi. VKİ değerleri ile Fazlalık VKİ Kaybı (FVKİK) hesaplandı. RDW değeri ile olan ilişki istatistiksel olarak incelendi. İstatistiksel analiz için SPSS v25.0 programı kullanıldı. p değeri 0,05'in altında anlamlı kabul edildi.
Bulgular: Çalışmaya 143 hasta katıldı. 32 hasta erkek, 111 hasta kadın idi. VKİ'ne bakıldığında ortanca değer erkekler için 46,2 kg/m2 (35,6-59,1 kg/m2), kadınlar için 47,2 kg/m2 (36-57,6 kg/m2) olarak saptandı. Hastaların ortanca yaş değeri 38 (17-68), ortanca RDW değeri %14,2 (%12-%19,7) idi. RDW ile FVKİK değerleri arasındaki ilişki Spearman Korelasyon Analizi ile değerlendirildi. Bunun sonucunda FVKİK1, FVKİK3, FVKİK6, FVKİK18 ve FVKİKm ile RDW arasında istatistiksel olarak anlamlı korelasyon saptandı (sırasıyla p=0,024, p=0,023, p=0,002, p=0,027, p=0,001). Korele olan değerler ile RDW yüzdeleri gruplandırılarak tekrar incelendi. FVKİKm, FVKİK3 ve FVKİK6'da RDW değeri 14,5 üstünde olan hastaların oranlarında istatistiksel anlamlılık saptandı. FVKİKm için anlamlılık değeri p=0,011, FVKİK3 için p=0,007 ve FVKİK6 için p=0,013 idi. 
Sonuç: Hastalarımızda bariatrik cerrahi başarı ile uygulanmış olup, tüm hastalarımızda kilo kaybı sağlanmıştır. RDW, bariatrik cerrahi sonrası takip eden yıllarda maksimum kilo kaybına ulaşma oranının (FVKİKm) bir öngörüsüdür. Klinik olarak faydalı, prognostik bilgi sağlayabilen, yeni bir preoperatif biyobelirteçtir. Fakat RDW, sadece prediktif olarak kullanılabilir. RDW ile kilo kaybı arasında mekanizma açık değildir. Bununla ilgili daha çok çalışmaya ihtiyaç vardır.

Abstract:
THE IMPACT OF THE PREOPERATIVE RED BLOOD CELL DİSTRİBUTİON
WİDTH VALUE ON WEIGHT LOSS ESTIMATION AFTER BARIATRIC
SURGERY: A RETROSPECTIVE STUDY

Introduction
Morbid obesity is a common health problem all over the world (1). Today, it is
considered as a serious problem that limits sociocultural life, increases mortality and
morbidity, and decreases the quality of life of individuals (2,3). Many treatment methods for
morbid obesity have been applied from past to present and it is a challenge to predict which
treatment method will be successful. Obesity surgery, which is major surgery, can cause
serious complications even though providing weight loss (4). Although mortality and
morbidity are not as much as obesity will cause in the future, bariatric surgery may also cause
mortality and morbidity (5). In addition, a predictive parameter has not yet been established
that indicates whether the operation will benefit the patient. If there was such a predictive
parameter, it would not be offered as a surgical treatment option to patients who are not
expected to benefit from surgery, and thus the patient would be protected from complications
of obesity surgery.
There are many studies on the predictive parameters of weight loss (6-9). The vast
majority of biochemical studies have been done with C-reactive protein (CRP), an
inflammatory marker (10). Another inflammatory parameter, like CRP, is erythrocyte
distribution width (Red Cell Distribution Width - RDW). It is a parameter that shows
anisocytosis, in other words, the volume change of erythrocytes. It is determined by a
complete blood count. It has traditionally been used in the differential diagnosis of anaemia
(11). RDW is considered as an indicator of both chronic inflammation and oxidative stres (11-
13). Many studies have been reported that RDW is a prognostic parameter in many diseases.
In our study, we aimed to evaluate whether RDW has a predictive impact on weight loss after
obesity surgery.

Material and Methods
This was a single-institution retrospective study using the electronic database at Ege
University. Ethics committee approval was obtained from the Medical Research Ethics
Committee of Ege University Faculty of Medicine (Decision number 19-5.2T/5, Decision
date: 29.05.2019). Patients who were decided eligible for obesity surgery in the Ege
University Multidisciplinary Bariatric Surgery Council between June 2011 and June 2019 and
who underwent sleeve gastrectomy or Roux en Y gastric bypass due to morbid obesity were
included in the study.
Patients who previously had another bariatric procedure were excluded from the study.
Finally, 143 patients who met the study criteria were included in the study.

Age, gender, comorbidity status, preoperative body mass index (BMI 0 ), type of
operation, BMI at 1, 3, 6, 12, 18, 24 months, lowest achieved BMI, current BMI and weight
regain were determined as study parameters and were statistically evaluated. The excess BMI
loss (EBMIL) was calculated with the BMI values in the outpatient controls.
In this calculation, the BMI value to be reached was taken as 25 kg/m 2 . BMI 0 was
determined as BMI in the preoperative period, and BMI t was determined as BMI at the month
of outpatient control. For the calculation of EBMIL t , the formula 100% * (BMI 0 -
BMI t )/(BMI 0 - 25 kg/m 2 ) was used. In this way, it was determined what percentage of the
excess BMI had been lost in the specified month for patients to reach 25 kg/m 2 .
Statistical analysis of the study was carried out with the support of Ege University
Faculty of Medicine, Department of Biostatistics and Medical Informatics. SPSS v25.0
program was used for statistical analysis. For the evaluation of the data, mean ± standard
deviation for numerical measurements in descriptive statistics, numbers and percentages for
qualitative measurements were used.
The relationship between RDW value and age, gender, comorbidity, BMI, EBMIL t
and weight regain was evaluated by Spearman Correlation Analysis. Covariance Analysis was
performed for the variables related to RDW. RDW value was grouped as ≤14.5% and
>14.5%. T-Test was used for independent variables. p<0.05 was considered significant.

Results
The mean values and standard deviations of the BMI, age and RDW values of the
patients are indicated in Table 1. The relationship between RDW, age, BMI 0 , EBMIL 1 ,
EBMIL 3 , EBMIL 6 , EBMIL 12 , EBMIL 18 , EBMIL 24 and EBMIL max were evaluated by Spearman
Correlation Analysis (Table 2). As a result of the analysis, a statistically significant
correlation was found between EBMIL 1 , EBMIL 3 , EBMIL 6 , EBMIL 18 , EBMIL max and RDW.
In addition, although there is a statistically significant correlation between EBMIL max and age,
and BMI 0 (p<0.05); There was no statistically significant correlation between RDW and age,
and BMI 0 (p=0.277 and p=0.06). Thus, it was observed that the correlation between RDW and
EBMIL max was independent of BMI 0 and age.
RDW values were evaluated separately (Table 3). Meanwhile, EBMIL 12 and EBMIL 24
parameters were not evaluated because they were not correlated with the Spearman
Correlation Test at the first stage. As a result, there were 103 patients with RDW values of
14.5% and below, and 40 patients with RDW values above 14.5%. The average RDW values
in the groups were 13.4% and 16.3%, respectively. Statistical significance was found in the
rates of patients with RDW value above 14.5 in EBMIL max , EBMIL 3 and EBMIL 6 . However,
although EBMIL value decreased with the increase in RDW level in other EBMIL values, no
statistical significance was observed. The significance value for EBMIL max was p = 0.011,
while p = 0.007 for EBMIL 3 and p = 0.013 for EBMIL 6 .

Discussion
In obesity treatment, weight loss is limited with methods such as diet, exercise and
medication, and long-term treatments increase the cost. In addition, regain of the weight in the
following period renders these treatment methods ineffective. Apart from the surgical
procedure, there is no chance of permanent and effective treatment (14). Surgical treatment of
patients should be managed by a multidisciplinary team.
Obesity surgery is major surgery. For this reason, care should be taken when referring
patients to surgery. Patients who will benefit from surgery should be well-identified. For this
purpose, many studies have been carried out in recent years on the predictive factors of
weight loss and comorbidities. Particularly, inflammatory parameters including RDW were
emphasized.
RDW is a measure of the change in the size of erythrocytes, reflecting the degree of
anisocytosis on the peripheral smear to the complete blood count. Numerous observational
studies have linked mortality and morbidity to a high RDW for many diseases. However,
RDW can only be an indicator of other negative prognostic factors such as age, comorbidities,
or physiological stress (15-21). These diseases are cardiovascular and cerebrovascular events,
venous thromboembolism, malignancies, sepsis, chronic obstructive lung disease, chronic
kidney disease and liver diseases.
The relationship between a high percentage of RDW and increased mortality and
morbidity has not been fully revealed. Pathophysiologically, RDW is considered to reflect
inflammatory status, oxidative stress and nutritional deficiencies (22,23). It is often thought
that inflammation and oxidative stress affect RDW by altering erythrocyte hemostasis. In
addition, it was found that the risk of metabolic syndrome and related long-term mortality
were higher in those with high RDW (24). Another study stated that RDW height is not
secondary to inflammation, but RDW increases as a result of a low-calorie diet applied during
bariatric surgery (25).
In our study, we tried to determine the relationship between RDW and BMI, and their
distribution by months and BMI which was calculated according to maximum weight loss.
For this reason, firstly, BMI of the patients was calculated before the operation. In addition,
the demographic characteristics of the patients such as age and gender were analyzed and in
the routine controls, the percentage of the weight they needed to reach 25kg/m 2 (EBMIL) was
calculated. Group distributions were homogeneous. However, EBMIL 1-3-6-12-18-24 values could be
reached in a decreasing number of patients since patients disrupted their routine controls.
EBMIL max value was taken into consideration more in the evaluation because of the
inaccessible data in the parameters of EBMIL 18-24 and the lowest weight reached by our
patients undergoing obesity surgery being detected at the 15.15 months. When the
relationship between RDW and EBMIL max , which is the main purpose of the study, was
evaluated, an inverse ratio was shown with RDW value and EBMIL 1-3-6-18-max . In other words, as
the RDW percentage increased, these values decreased. As a result of this statistically
significant parameter, data was evaluated by covariance analysis, considering that RDW may
have been affected by other parameters. For similar reasons, covariance analyses were

performed between RDW and only EBMIL max . As a result, it was seen that the correlation
between RDW and EBMIL max was independent of age and BMI 0 . In another study (26)
comparing RDW with EBMIL 6-12 , RDW was associated with EBMIL 12 as a result of
multivariate analysis.
The normal range for RDW is 11.5% to 14.5%. There are hardly any situations where
RDW is lower than normal. In our study, we took this reference value into consideration
while deciding the cut-off value of RDW. We analysed the patients in two groups as groups
with RDW values of 14.5 and below and above 14.5. RDW, which has a cut off value, can
make it easier to predict postoperative weight loss. As a result of the statistical analysis
performed after grouping, it was observed that EBMIL max decreased in those with RDW value
above 14.5.
There are few studies in the literature that investigated the use of RDW in obesity
surgery. Our results are similar to the study of Wise et al.(26). However, in our study, the
follow-up period was longer and the EBMIL max value was statistically evaluated accordingly.
And also the distribution by months was examined in more detail. These are the positive
aspects of our study.
It should be kept in mind that RDW can be affected by inflammatory parameters, as
well as many other parameters such as anaemia and haemorrhage. Vaya et al. (27) reported
that elevated RDW in obese patients does not reflect systemic inflammation because it is not
associated with other inflammatory markers. In our study, the haemoglobin level which show
anemia and C reactive protein level which shows inflamation, were not evaluated. This
condition can be considered as a shortcoming of the study.

Conclusion
In conclusion, preoperative RDW is an indicator to predict the maximum weight loss
rate (EBMIL max ) in the following years after sleeve gastrectomy and Roux en Y gastric bypass
surgeries. It is a new preoperative biomarker that can provide clinically useful prognostic
information. But RDW can only be used predictively. The mechanism between RDW and
weight loss is still not clear.
In addition, the preoperative RDW value may be affected by conditions such as a
temporary inflammatory response, haemorrhage or blood transfusion.
Other inflammatory parameters, bleeding status, preoperative anaemia and treatment
of anaemia, blood transfusion and other diseases that may change RDW should also be
evaluated later in the study. In addition, the number of patients should be increased and
follow-ups should be more strict.