Chronic kidney disease acquired knowledge in a diabetic and hypertensive population using a translated and validated questionnaire

Abstract

Chronic kidney disease (CKD) is the progressive and irreversible functional and/or structural impairment of the kidney; its main etiologies include hypertension and diabetes. Mexico has the second highest prevalence of CKD worldwide with a high economic burden affecting public and private health systems. Patients with higher knowledge about CKD increase their adherence to preventive treatment. In this study we aim to describe the knowledge of CKD in a sample of Mexican high-risk population, comparing it with general Mexican population, medical students and nephrologists. A cross-sectional, observational study was performed divided in two phases: translation and validation of the knowledge questionnaire to Spanish, and cross-sectional survey to evaluate the knowledge of CKD in patients with diagnosis of diabetes and/or hypertension. We interviewed medical students, general population, and nephrologists to attain validation of the questionnaire in Spanish. The questionnaire was answered by 1,061 participants within the high-risk population. The results of the questionnaire were: 22/24, 18/24, 13.8/24, and 13.4/24 in nephrologists, medical students, normal subjects, and high-risk population, respectively. The questions with least correct answers were related to kidney functions and CKD risk factors. To our knowledge this is the first time a questionnaire for CKD knowledge is applied in Mexican population. These findings suggest poor understanding of kidney functions, risk factors, and symptoms of CKD. It is important not only to provide medical treatment to chronic illness but also awareness of the consequences of not achieving goals of treatment.

Keywords:

• Chronic kidney disease
• diabetes
• hypertension
• knowledge
• questionnaire
• public health

Introduction

Chronic kidney disease (CKD) is the progressive functional and/or structural impairment of the kidney for at least three months [1]. CKD is classified in a spectrum of levels determined by the glomerular filtration rate (GFR) and the presence and degree of proteinuria [2]. This pathology culminates in the requirement of renal replacement therapies (RRT) which include hemodialysis, peritoneal dialysis or renal ­transplant [3]. CKD is considered the 16^th cause of years of life lost, and its main etiologies include hypertension and diabetes [1,2].

It affects 8–16% of the population worldwide and accounts for 12.2 deaths for every 100,000 individuals [4–8]. Due to a constant increase in the incidence and prevalence of CKD, several preventive strategies have been studied to delay its progression [3].

Mexico has the second highest prevalence of CKD worldwide [9]. The high percentage of diseases associated with CKD such as obesity, diabetes mellitus, and hypertension further hurdle the country’s social, and economic development [10]. The economic burden of CKD rises as the disease progresses. The annual budget per patient increases from $7,537–8,091 to $36,969–46,178 USD as they reach stage 4–5, up to $121,948 by commercial insurance companies and up to $87,339 in public programs with the initiation of RRT [11]. In Mexico, CKD is the seventh cause of death and RRT represents an expenditure close to 196 million USD [12]. Furthermore, RRTs have important environmental costs. A single session of hemodialysis generates 2.5 kg of residual byproduct and requires a steep volume of water [13]. Moreover, due to the myriad of inert pathophysiological complications, there is a rise in hospitalization, and cardiovascular risk [14]. Mortality is 57% higher in patients with <60 mL/min of GFR and 63% higher in those with microalbuminuria when compared to patients without CKD. The natural progression of the disease, erythropoietin deficiency, acid-base alterations and mineral bone disease further strain this population.

Previous research has shown that patients with higher knowledge about CKD increase their adherence to preventive treatments [4]. Moreover, it has been studied that patients do not recognize the risk factors for CKD, signs and symptoms or basic kidney functions [5,6]. White et al. designed a questionnaire to test CKD knowledge and reported that patients with high-risk of progression to renal failure had insufficient insight of the basic kidney functions [8]. Gheewala et al. found similar results [15]. In this study we aim to describe the knowledge of CKD in a sample of Mexican general population who live with hypertension and/or diabetes, and to compare it with knowledge of the general Mexican population, medical students and nephrologists.

Methods

This study was carried out with prior review and approval of the Internal Ethics Review Board and Science Committee with the approval number P000359-ERCUEST-CEIC-CR002. It adheres to institutional and national regulations as well as those established in the Helsinki Conference of 1964 and its revision in 2012.

Design and setting

A cross-sectional, observational study was performed divided in two phases: translation and validation of the knowledge questionnaire to Spanish and cross-sectional survey to evaluate the knowledge of CKD in patients with diagnosis of diabetes and/or hypertension.

For the first phase we performed a translation and cultural adaptation from English to Spanish of the questionnaire used by Gheewala et al. [15]. This translation process was adapted from Mota et al. [16] and is synthesized in Figure 1.

Figure 1. Synthetized translation process of the questionnaire.

We interviewed medical students, general population, and nephrologists to attain validation of the questionnaire in Spanish. Each item was answered by 29 nephrologists, 26 students and 134 members of the general population without DM, HTN or CKD. The interviews were done during physiology classes, specialist conferences and public spaces respectively and the answers were collected using Google Forms. The questionnaire consisted of 24 questions with a ‘yes’ ‘no’ and ‘I don’t know’ answer, this last one was counted as incorrect and given a score of zero.

Statistical analysis

Reliability of the questionnaire was measured by calculating Cronbach’s alpha. Normality of distributions for the continuous variable was determined using Shapiro-Wilk test. Kruskal-Wallis test was used to determine if there were any statistically significant differences between the knowledge scores of the three groups. The whole statistical analysis was performed using SPSS (2021) statistical software [17].

The second phase consisted in the major diffusion of the questionnaire. We included patients 18 years or older diagnosed with hypertension and/or diabetes mellitus who were able to answer a questionnaire on their own. All data was collected through a survey using Google Forms from May 14th 2021, to June 21th 2021. The survey was distributed using social media platforms via an unrestricted snowballing strategy.

Study variables

The maximum score for the questionnaire was 24 points (1 point per item), divided in 5 sections: general knowledge, kidney function, renal assessment studies, risk factors for kidney disease and signs and symptoms of CKD (Table 3). Each question had multiple-choice answers with true, false and I do not know options. Additional information included previous diagnosis of hypertension or CKD and current treatment with RRT. For phase 1 an additional question inquiring the status of medical student or nephrologist was included.

A screening for duplicate responses was carried out comparing each response to those within a range of 3 min or 5 responses. The positive responses for previous diagnosis of CKD were not considered for the analysis.

Results

Phase 1

The questionnaire was answered by 29 nephrologists, 26 students and 134 from the general (non-sick) population. We obtained a Cronbach’s alpha of 0.89, demonstrating an adequate internal consistency. To evaluate the distribution a Shapiro-Wilk test was performed and a p-value of <0.05 for each group was obtained, indicating data is not normally distributed; therefore, nonparametric statistical tests were used to perform subsequent analyses. Kruskal-Wallis test revealed p < 0.0001. The median total scores of the nephrologists, medical students and public were 22, 18, and 13.8 out of 24, respectively. With the results of these tests we determined validity of the translated questionnaire and proceeded with phase 2.

Phase 2

The questionnaire was answered by 1,061 participants within the high-risk population (subjects with a chronic illness), all older than 18 years. Of the 1,061 patients in this phase, 398 (37%) had DM, 776 (73%) had HTN, 41 (3%) had CKD, and 8 were currently under RRT (<1%) (Table 1). The results of the questionnaire were: 22/24 in nephrologists with a standard deviation (SD) 1.2, 18 in students with a SD of 2.7, 13.8 in normal subjects with 3.9 SD and 13.4 in high risk population with 4.5 of SD (Table 2 and Figure 2). We performed single factor ANOVA tests per question to determine statistical difference among the 4 groups (Table 3).

Figure 2. Answers by each group. Correct answers: 22/24 in nephrologists with a standard deviation (SD) 1.2, 18/24 in students with a SD of 2.7, 13.8/24 in normal subjects with 3.9 SD and 13.4/24 in high risk population with 4.5 of SD.

Table 1. Demographics of population at risk.

	Number of high-risk patients (% of total, 1061)
Diagnosed with hypertension	776 (73)
Diagnosed with diabetes mellitus	298 (28)
Diagnosed with hypertension and diabetes mellitus	275 (26)
Diagnosed with chronic kidney disease	41 (4)
Renal replacement therapy (peritoneal dialysis, hemodialysis, renal transplant)	8 (1)

Table 2. Results of the questionnaire by group.

	n	Correct out of 24; mean (%)	SD	Median	Minimum	Maximum	Range
Nephrologist	29	21.9 (91.25)	1.205	22	19	24	5
Medical students	26	18.23 (75.96)	2.74	18	14	23	9
Non-risk population	134	13.84 (57.67)	3.96	14	3	22	19
High risk population	1061	13.4 (55.83)	4.5	14	0	24	24

SD: standard deviation.

Table 3. Questionnaire responses divided by group.

		Correct (%)
Item	Question:	Nephrologists (n = 29)	Students (n = 26)	Low-risk (n = 134)	High-risk (n = 1061)	p Value
1*	A person can lead a normal life with one healthy kidney.	100.00	96.15	91.04	83.60	<0.01
2	Herbal supplements can be effective in treating chronic kidney disease.	100.00	57.69	18.66	34.87	<0.01
3*	Certain medications can help to slow-down the worsening of chronic kidney disease.	96.55	96.15	67.16	68.71	<0.01
What functions do the kidneys perform in the body?
4*	The kidneys make urine.	100.00	92.31	62.69	62.11	<0.01
5*	The kidneys clean blood.	100.00	96.15	66.42	82.00	<0.01
6	The kidneys help to keep blood sugar level normal.	34.48	19.23	41.04	33.46	0.13
7*	The kidneys help to maintain blood pressure.	100.00	100.00	36.57	47.41	<0.01
8	The kidneys help to break down protein in the body.	51.72	61.54	41.79	24.22	<0.01
9*	The kidneys help to keep the bones healthy.	100.00	76.92	20.15	20.26	<0.01
Which of the following are commonly used to determine health of the kidneys?
10*	A blood test.	100.00	92.31	51.49	69.37	<0.01
11*	A urine test.	100.00	100.00	93.28	88.50	0.02
12	A fecal (poo) test.	96.55	92.31	65.67	67.48	<0.01
13*	Blood pressure monitoring.	72.41	80.77	23.88	33.08	<0.01
What are the risk factors for chronic kidney disease?
14*	Diabetes.	100.00	100.00	80.60	81.06	<0.01
15	Being female.	75.86	38.46	87.31	73.42	<0.01
16*	High blood pressure.	100.00	100.00	56.72	65.32	<0.01
17*	Heart problems such as heart failure or heart attack.	100.00	92.31	38.81	38.55	<0.01
18	Excess stress.	68.97	11.54	39.55	29.50	<0.01
19*	Obesity.	100.00	88.46	68.66	66.82	<0.01
What are the signs and symptoms that a person might have if they have advanced chronic kidney disease or kidney failure?
20*	Water retention. (excess water in the body)	100.00	88.46	92.54	89.26	0.18
21	Fever.	93.10	23.08	47.01	25.45	<0.01
22*	Nausea/vomiting.	100.00	73.08	40.30	38.55	<0.01
23*	Loss of appetite.	100.00	57.69	49.25	42.13	<0.01
24*	Increased fatigue (tiredness).	100.00	88.46	78.36	74.93	<0.01

The three questions with the lowest correct rate of each group are highlighted in red.

The three critical questions were different in each group (Table 3). Among nephrologists, 34% answered true to ‘The kidneys help to keep blood sugar level normal’ (the correct answer is false). The two other question with the lowest correct rate were: ‘The kidneys help breakdown proteins in the body’ (51%) and ‘Excess stress is a risk factor for CKD’ (69%). The correct answer is false for both.

The questions with the lowest correct rate were similar in the medical student group, except the percentage of students answering correctly was lower. ‘Excess stress is a risk factor for CKD’ and ‘The kidney helps to keep blood sugar levels normal’ were answered correctly by 11% and 19% of students, respectively. The third question with the lowest correct rate in the medical student group was: ‘fever is a sign of CKD’ (23%). The correct answer is false.

The three answers with the lowest correct rate in the non-risk group were: ‘Herbal supplements can be effective in treating chronic kidney disease’. (19%), ‘The kidneys help to keep the bones healthy’. (20%), and ‘Blood pressure monitoring’ to determine kidney health (24%).

The three questions with the lowest correct rate among the high-risk group were: ‘kidneys help maintain bones healthy’ (20%), ‘The kidneys help breakdown proteins in the body’ (24%), and ‘fever is a sign of CKD’ (25%). Other notable questions that were answered incorrectly by the high-risk group pertain to the tests/interventions available to determine kidney function and the risk factors for kidney disease. Among the high-risk group, 33% correctly answered that blood pressure monitoring can be used to determine kidney function, and 39% correctly answered that heart disease is a risk factor for CKD. Additionally, 35% of subjects in the high-risk group answered correctly that herbal supplements are not effective in treating kidney disease. The complete results of the questionnaire by group can be found in Table 3.

Discussion

To our knowledge this is the first time a questionnaire for CKD knowledge is applied in a Mexican population. The findings suggest poor understanding of kidney functions and factors for CKD or its progression. It is necessary to acknowledge that improving this knowledge should increase awareness of CKD and prevent or delay its progression [6]. There was a consistently incorrect answer among the nephrologist group about glucose and the kidney. This could be explained perhaps due to a language misunderstanding, since kidneys do not help maintaining blood sugar levels, but they do have a participation in preventing hypoglycemic events, while a patient with CKD and DM has a higher risk of hypoglycemia through different mechanisms such as reduced renal elimination of insulin [18]. The controversy surrounding this question might also be explained by the paradoxical finding that glycemic levels improve in patients with late stages of CKD, as described by Kalantar-Zadeh et al. [19]. Another question that was controversial was #8, regarding the role of the kidney in the metabolism of proteins. There is evidence of the role of the proximal tubule in the metabolism of albumin, as highlighted by Molitoris et al. [20]. Although this study was published after the questionnaire was distributed to nephrologists, other previous studies have described similar findings [21]. These findings in the literature may partially explain the low scores obtained by nephrologists in these two questions.

Mexico lacks regulation about commercialization and distribution of herbal medicines and supplements, and it is important to notice that 2 out of 3 Mexicans believe that herbal supplements may be suitable treatments for CKD, which is similar to underdeveloped countries (70–80%) and a lot more than in developed countries (20%) [7]. These herbal supplements go from plants to manufactured pills as Herbalife, which do not require approval from COFEPRIS, the office that regulates medical drugs in Mexico [22]. Some of these treatments have substances that have been identified as harmful for the kidneys leading to tubulointerstitial damage [23,24].

Since the early 2000s, we are living in an era where multiple drugs have shown to delay the progression of CKD [25,26]. According to our findings two out of three patients seem to know this, but this does not necessarily show that they know how to access these drugs, even though some of them are available in the public health system. We have angiotensin converting enzyme inhibitors and angiotensin II receptor blockers, that are used for HTN, and to help control proteinuria in CKD. Perhaps, if our theory is that if patients not only know, but understand the effects of key medications, adherence to treatment could be improved. New treatments are available for DM, which include SGLT2 inhibitors that have shown to delay not only CKD related to DM [27], but also CKD from glomerular diseases and heart failure even in patients without DM [28,29]. Unfortunately, not all of them are widely available in the public health system, or represent an out-of-the-pocket expense for the patient, which most of the time cannot even be paid.

Obesity is an important risk factor for CKD, where 67% of the population seem to acknowledge this. As seen in ENSANUT, in Mexico we have one of the highest index of overweight and obesity with 75.1% of population and it has been increasing with the years [10,30]. Even though more than half of the population knows the situation, there are scarce to none interventions in a dietary approach to prevent and/or reduce obesity and treat CKD [31].

CKD does not show symptoms until advanced stages [2], and some of the symptoms are not clear for the population. For example, 3 out of 4 patients with chronic illness believe that fever is a sign of CKD which is false and less than half of the population is aware about nausea, vomiting and lack of appetite being symptoms of CKD. Since CKD could be asymptomatic in the first stages [32,33], it is important to promote annual checkups with analysis of creatinine, urianalysis and blood pressure monitoring once a year as indicated by international [34] and Mexican guidelines [35].

Limitations

We acknowledge the following limitations of our study. We did not control variables such as age, sex, educational level, occupation, socioeconomic status, income, religion, marital status, among others. All these are factors that could impact the statistical analysis, especially in the high-risk group (diabetes and hypertension subjects). For the same reasons, we acknowledge that our study sample may not be an accurate representation of the Mexican population at high-risk of developing CKD. Two questions (#6 and #8) were answered wrong by several nephrologists. We expanded on this matter in the Discussion section above but would like to emphasize that there may not be a right or wrong answer for those two questions. Furthermore, patients may find motivation in several other sources to drive changes that improve their health and wellbeing, not only in how much knowledge they harbor about their disease. For example, medication side effects, religion, their relationship with their health care provider, among others, are known to impact adherence to treatment. These factors were not evaluated in our study and should be the focus of future studies.

Conclusion

This questionnaire has shown to be validated in a Spanish-speaking population. The knowledge of the Mexican population of the functions of kidneys and CKD symptoms is poor. Two out of three Mexicans believe that herbal supplements may be suitable treatments for CKD, which is similar to underdeveloped countries. Two out of three patients seem to know that multiple drugs may delay the progression of CKD, but not all of them are widely available in the public health system affecting the access and adherence. 67% of the population knows that obesity is an important risk factor, but there are scarce interventions to prevent and reduce the risk. Symptoms of CKD are not clear for population. It is important not only to provide medical treatment to chronic illness but also awareness of the consequences of not achieving goals of treatment. Some public health programs could help to be aware of CKD, its risk factors, prevention, and the impact it has on public health.

Abbreviations
CKD	=	Chronic Kidney Disease
DM	=	Diabetes Mellitus
ESKD	=	End Stage Kidney Disease
GFR	=	Glomerular Filtration Rate
HTN	=	Hypertension
KDIGO	=	Kidney Disease Improving Global Outcome
RRT	=	Renal Replacement Therapy

Acknowledgements

The authors thanks to Alexa, Julia, Julio, Andrea, and Samuel for translating the original questionnaire. We acknowledge the support of the Institute of Obesity Research. We deeply appreciate their contribution to our work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.