Chronic kidney disease (CKD) is a public health problem that causes morbidity and mortality and high costs, with a very variable incidence and prevalence among countries, with scarce information in stages prior to dialysis, remaining as an underdiagnosed and late reference disease.

Objectives: To estimate the frequency of kidney damage in adults with hypertension in the Family Medicine Unit (UMF) Number 28 of the Instituto Mexicano del Seguro Social (IMSS).

Methods: A descriptive, observational, cross-sectional and prospective study was carried out, including 164 randomly selected individuals with hypertension, who were evaluated for renal function with the estimation of Glomerular Filtration Rate with the Chronic Kidney Disease-Epidemiology Collaboration formula (CKD-EPI), and the Albuminuria/Creatinuria Ratio (ACR), stratifying kidney disease according to the recommendations of the Kidney Disease Improving Global Outcomes foundation. Descriptive statistics were used with the statistical program SPSS v21.

Results: The frequency of CKD was 6.70%, lower than that reported in other investigations.

Conclusion: This research reports the lowest frequency in the literature, with the use of two detection methods that help reduce the under-diagnosis of kidney disease, since in routine clinical practice only Glomerular Filtration Rate in the assessment of renal function is estimated, highlighting the importance of an internationally standardized assessment.

Keywords: kidney diseases, hypertension, albuminuria, descriptive statistics, chronic kidney disease, creatinuria ratio, routine clinical practice, glomerular filtration rate, collaboration formula

Chronic Kidney Disease (CKD) is defined as the presence of alterations in renal structure or function for more than three months and with implications for health,¹ it is considered a public health problem that causes morbidity and mortality and high costs,^2,3 and it occupies the 27th place in the list of causes of mortality worldwide, with an incidence and prevalence of end-stage renal disease that differs substantially between countries and regions,^4,5 the available information on CKD in stages prior to dialysis is scarce, remaining a disease underdiagnosed and with late referral.^2–6 The risk of developing CKD is increased in some people in whom a greater effort should be made in the early detection of this condition, especially in those with Diabetes Mellitus (DM), Systemic Arterial Hypertension (SAH), over 60 years of age, and with a family history of CKD. With regard to SAH defined as: a sustained increase in blood pressure with figures ≥140 / 90 mmHg with adequate measurement techniques, or greater than or equal to 130/80 mmHg according to the literature reviewed.^7–10 According to the National Survey of Health (ENSANUT) 2012 a prevalence of hypertension in Mexico of 31.5% in the general population was reported, rising in adults with obesity to 45.3% and higher in adults with diabetes up to 70.7%, observing hypertensive adults 47.3% did not know that they suffered from hypertension.¹¹ The evaluation of renal function is carried out by means of the estimation of Glomerular Filtration Rate (GFR), currently the method of estimation of the GFR is recommended with the CDK-EPI,^1–12 and by means of the determination of the ACR (Albuminuria/Creatinine Ratio), considering that the proteinuria is a marker of established renal damage and plays a direct pathogenic role in renal and cardiovascular progression,^1–6 the standard measurement has usually been the quantification of urine collected during 24 hours, to avoid errors in the collection, the determination of the ACR is recommended, which currently allows us to integrate the classification of the CKD together with the estimation of the GFR.^1–6 Salvador et al.,¹³ in Catalonia report a frequency of CKD of 18.8% in patients with SAH over 60 years of age,¹³ Da Silva et al.,¹⁴ in Brazil, found a prevalence of CKD of 38.6% in patients with SAH,¹⁴ Sánchez et al.,¹⁵ in Mexico, found a 6% frequency of CKD in patients with SAH.¹⁵ Considering the wide variability in the frequency results of CKD, and the importance of early intervention in early and timely diagnosis, to reduce the progression of kidney disease, improve survival and quality of life, as well as decrease in costs of the treatment, the objective of this study was to estimate the frequency of kidney damage in adults with SAH in UMF 28 of IMSS in 2017.

The nature of the study is observational, descriptive, cross-sectional and prospective. Data was obtained from records of adult patients between 18 and 80 years of age, with a diagnosis of arterial hypertension who attended consultations at the UMF Number 28 of IMSS in Mexicali Baja California, from August 2017 to January 2018.

 Sample size

The sample size was calculated for a simple random sampling by attributes, considering that in our medical care unit there is a population of 167,552 individuals. The sampling frame consisted of all patients diagnosed with SAH without other comorbidities in the UMF 28, with a total of 11,040 patients. The formula for estimating a proportion in a finite population, a confidence interval of 95% was considered, accuracy in the estimation of 5%, and a prevalence value in the literature of 12%^16–18 for CKD in patients with SAH.

$n=\frac{N Z_{\alpha }^2 p \left(1-p\right)}{d^2 \left(N-1\right) + Z_{\alpha }^2 p \left(1-p\right)}=160 patients$

The inclusion criteria were adults older than 18 and younger than 80, and those without comorbidities that could reflect a rise in proteinuria (heart failure, collagen disease, DM). Patients with incomplete laboratory analysis results were excluded.

Obtaining information

Primary care clinics records of patients with SAH without other comorbidities who attended the consultation during the study period were randomly selected; 4 patients per clinic of the 44 existing clinics in the FMU number 28 were randomly included, with a total of 174 of which 12 patients were excluded due to insufficient information, with a final sample of 164. Each patient was informed by their doctor about the need to perform laboratory tests to evaluate kidney function. As a first step, in the unit’s laboratory, serum creatinine was determined using a standardized modified Jaffé method,¹⁹ as well as the determination of albuminuria and creatinuria with the turbidimetric method of immunoinhibition.^19,20 In a second stage, three months later, the determinations were repeated in those patients in whom biochemical alterations were found. Evaluation of renal function was performed with the estimation of the GFR with the formula CKD-EPI,¹² and the ACR, stratifying the kidney disease according to the recommendations of the KDIGO.¹ The study variables were: estimated GFR, the ACC, age, gender, body mass index, and the years since the diagnosis of SAH.

Statistic analysis

For the information analysis, descriptive statistics were used: measures of central tendency and dispersion for quantitative variables and percentages for qualitative variables. The software used was SPSS version 21. This study does not contradict the guidelines of the Ley General de Salud en Materia de Investigación para la Salud (General Law of Health in the Matter of Research for Health) and with local norms and manuals.

Table 1 presents the general characteristics of patients with SAH in the sample. For the total number of patients included, the average age was 58.51±12.7 years, with an average disease time of 8.99±9.5 years, and an average BMI of 31.5±5.5 kg / m2. By gender, 62% were women and 38% men. Of the patients studied, a CKD frequency of 6.70% (11 patients) was found whose general characteristics are presented in Table 2, classified by gender. Regarding GFR, an increased frequency was observed in the G3a category, and in the category of persistent albuminuria A2 was more frequent. The age with the greatest presence of CKD was in those older than 50(10/11). Of the total number of patients diagnosed with CKD, 7/11 resulted with abnormal GFR. However, when the ACR was included as a diagnostic complement, of the 7 patients with abnormal GFR, 2 showed altered ACR values. But 4 patients resulted with altered ACR (4/11) and normal GFR, which routinely leaves 36% of patients with under diagnosis of CKD.

Discussion

Conclusion

Acknowledgements

Conflict of interest

References

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