IJCRR

IJCRR - 5(21), November, 2013

Pages: 83-91

Date of Publication: 21-Nov-2013

DIAGNOSIS OF IRON DEFICIENCY OF CHRONIC KIDNEY DISEASE : VALIDITY OF IRON PARAMETERS, RETICULOCYTE HEMOGLOBIN CONTENT(CHR) AND HYPOCHROMIC RED CELLS IN INFLAMMATORY STATE

Author: Vidyashankar P., Alan F. Almeida, Niwruti K. Hase, Arun Halankar, Harinakshi Rai, Sadanand Bhusari

Category: Healthcare

Abstract:Introduction: Diagnosis of iron deficiency is difficult in presence of uraemia. The validity of these tests in the presence of inflammation has not been studied, and it formed the basis of this enquiry. Methods: On hundred and twenty two consecutive chronic kidney disease (CKD III, IV, V-non dialysis) patients were enrolled. Complete hemogram, iron studies, Reticulocyte hemoglobin content (CHr) and percent hypochromic red cells (%Hypo), high sensitive CRP (hs-CRP) levels were done. In the study group of 122 patients screened, 103 patients were found to be iron deficient by Kidney Dialysis Outcome Quality Initiative (KDOQI) criteria. In the iron deficient patients, intra venous iron (i.v iron sucrose 1000mg) was administered in divided doses followed by erythropoetin and the tests were repeated after 4 weeks of completing i.v iron therapy. If the rise in Hb> 1gm%, at the end of 4 weeks, the patient were grouped into responders (iron deficient subjects). The rest were grouped as non responders(Iron replete).The value of the tests, individually or in combination, was determined in the subgroups and categorized based on hs-CRP levels (< 5mg/L). Results: Fifty eight of the 103 patients responded to i.v iron therapy (iron deficient).Varied sensitivity, specificity, and positive and negative predictive values were noted when tests were used individually or in combination to diagnose iron deficiency anemia. Conclusion: Iron studies are useful screening methods, but In the presence of inflammation, the combination of parameters with CHr and Hypochromic red cells add to specificity.

Keywords: Iron deficiency, iron studies, Reticulocyte hemoglobin content (CHr), Hypochromic red cells (Hypo %), Inflammation.

Full Text:

INTRODUCTION

Diagnosing iron deficiency with currently available tests is rendered difficult in patients with chronic kidney disease due to presence of inflammatory state associated with uremia [1,2,3,4,10]. The accurate diagnosis of iron status is essential in avoiding iron overload, which increases morbidity and mortality.   Serum ferritin and transferrin saturation (TSAT) are commonly and easily available tests [12,13,14] for diagnosis. However, serum ferritin is an acute phase reactant, and is raised in the anemia of chronic disease and uremic state, hence these values could be unreliable [3,12,13,33,34].    

Newer markers like CHr and hypochromic red cells have been currently introduced to guide iron therapy [18,19,20,26,38,39]. European best practice guidelines 2005 [8,17,27] and K/DOQI 2006 guidelines have  recommend these newer parameters, Reticulocyte hemoglobin content (CHr) and Hypochromic red cells (Hypo %) as marker of iron deficiency status. [7,8,9,21,22,23]. But these tests have not been validated in the presence of inflammation ,which is often found in azotemic and hemodialysis patients [11,12,32].

CHr and hypochromic red cells has been shown promising evidence in studies by Fishbane S et al and Cullen P [18,20,22,35,41]. Their validity in inflammatory state have not been evaluated.

There is no single test or in combination have good validity in diagnosis of iron deficiency (34). Hence, poor response to intravenous iron is considered as the gold standard in the diagnosis of iron deficient state (32,33,40,43,50)

SUBJECTS AND METHODS 

     Patients and study protocol

     A Prospective study was conducted at King Edward VII Memorial Hospital affiliated to Seth GS medical college, Mumbai, India. We included 122 (70 males and 52 females) consecutive patients with chronic kidney disease (Stage 3, 4 and 5 not on dialysis) attending the Nephrology outpatient services. Institution ethical committee approval and informed consent were taken before enrollment. Patients with age < 18 years, recent blood transfusions (Preceding 2 months), with active infection, bleeding, malignancy and active liver disease were excluded. After a wash out period of seven days (on oral iron preparation) and for 14 days (on intravenous iron preparation), fasting blood sample was collected and tested for the following parameters . Iron studies including serum iron, TIBC, transferrin saturation and ferritin. Reticulocyte parameters like absolute reticulocyte count (ARC), reticulocyte percentage, corrected reticulocyte index (CRI), reticulocyte hemoglobin content (CHr) and hypochromic red cells (Hypo%). High sensitive C - Reactive Protein (hs-CRP). Blood urea nitrogen, Serum creatinine, Serum electrolytes, urine examination, urine culture, liver function tests. The patients were diagnosed to have iron deficiency if they have one of the following  as per Kidney Dialysis Out  come Quality Initiative (K/DOQI) criteria (Transferrin saturation (TSAT)< 20 % or Serum ferritin<100 ng/mL) [9,45]. Patients with any one of the above were presumed to have iron deficiency   state and were given 1000mg of intravenous iron sucrose to replete the iron stores [8,9,51]. Iron deficient patients were given erythropoietin after repletion of iron stores, initially with the dose of 100 to 150U/kg/week and increments were made accordingly to get maximum response [9].

Red cell parameters, CHr, Hypochromic red cells and iron studies  mentioned above was be repeated 4 weeks of completing last dose of iron therapy as applicable .Response to iron was defined as, if  they satisfy one of the criteria ( increase in Hemoglobin by ≥1 gm at the end of 4 weeks [20,22,29,40,44,46]. Patients with response intravenous iron were presumed to have iron deficiency state and were taken as a gold standard in comparing various test parameters [32,39,40]. Non responders are those who did not fulfill the above mentioned criteria and were presumed to be iron replete. Patients were grouped into the absence or presence of inflammation based on hsCRP cut off  ≤ 5 mg/dl o r> 5 mg/dl respectively [40,43].

Laboratory methods

The samples for the complete blood count, CHr and hypochromic red cells was processed within 3 hrs of collection. The reticulocyte parametres like CHr absolute reticulocyte count, reticulocyte percentage was processed by ADVIA 120 automated hematology analyzer (Bayer’s diagnostics) at Ranbaxy research laboratory [37, 42]. The reticulocytes were stained with RNA stain oxazine 750 and analyzed by flow cytometric principle with proper standardization. Serum ferritin was tested by Enzyme Linked Iimmuno Sorbant Assay technique, iron studies done by colorimetric methods using SESOMEM analyzer. C - Reactive Protein was be measured by immunonephelometric method at the Immunology laboratory department of pathology. Blood urea nitrogen, serum creatinine, serum electrolytes, urine examination, urine culture, liver function tests, viral markers were done at hospital central clinical laboratory.

Statistical analysis

Statistical analysis was performed using the computer software package of social science (SPSS 13.1, 2005: SPSS Inc, IL, USA.) The data was expressed as mean ± Standard Deviation. Comparison of data for responders and non responders were performed by using the t-test or Mann-Whitney U-test as applicable. The inter group comparison was made by analysis of variance test (ANOVA). The sensitivity and specificity, positive and negative predictive values were calculated using appropriate formula. A p value of less ? 0.05 was considered as statistically significant.

RESULTS

There were 64 males with mean age of 45.32?12.23 years and 39 females with mean age of 41.23?10.34 years were iron deficient.  A total of 103 patients were iron-deficient by KDOQI criteria (TSAT < 20% or Serum ferritin <100mg/dl)  According to the response criteria mentioned in the study methods,58 (56.31%) patients  were iron deficient and 45 (43.68%)  were Iron replete as shown in the table 1 and 2.

The base line mean parameters among each sub groups were compared. Parameters like hemoglobin (Hb), TSAT, reticulocyte count (Ret ct), Hypo%, hs CRP (P<0.005), serum iron, TIBC, CHr (P<0.05) were statistically significant among iron deficient and iron replete subjects as shown in table 1.

The sensitivity, specificity, positive and negative predictive values of various tests and their combination is shown in table 3

  DISCUSSION

Iron deficiency is the major cause of inadequate response to erythropoeitin therapy in patients with chronic kidney disease. The accurate and early detection of iron deficiency is the most essential step in the management of the patients with chronic kidney disease. However, the diagnosis of iron deficiency in patients with chronic kidney disease is rendered difficult as the currently available tests are less reliable in presence of uremia (inflammatory state) [4, 5]. Measuring reticulocyte hemoglobin content (CHr) and hypochromic red cells (Hypo%) has been proposed as a measure of available iron stores that could be superior to the available tests in various studies[29,30,42,43,47,48].

In this study we specifically investigated for the validity of iron parameters (Serum Ferritin and Transferrin saturation (TSAT), CHr and hypo% in the diagnosis of iron deficiency state in the presence of inflammation. We compared newer parameters with iron studies, and the combination of both parameters taking chosen cut off value of each parameter.In study by Kalantar-Zadeh et al, serum ferritin cut off off < 200ng/ ml had sensitivity of 41 % and specificity of 100 %, TSAT cut off< 20 % had sensitivity of 88 % and specificity of 63 %[14]. In a study by Hesegawa et al (40) found similar predictive power various test parameters as in hemodialysis patients, but the validity of these parameter in the presence of inflammation has not been evaluated . In similar studies by Tessitoire et al[50], in non dialyzed patients, the sensitive of CHr varied from 58.67% to 84.5% and specificity of 78.88 to 88.67%.Validity of theses tests in the presence of inflammation has not been evaluated .

In Hemodialysis   patients, a study by Chuang CL et al, had diagnostic sensitivity and specificity of ferritin < 100ng/ml and TSAT < 19 % of 68.6 % and 60.8 % respectively [44]. The efficiency of both tests when used in combination was 64.0 %.When only ferritin <100 mg/ml was taken the diagnostic criteria, sensitivity and specificity was 35.3 % and 78.4 % respectively. The TSAT <19 %, had diagnostic sensitivity and specificity of 58.8 % and 60.8%respectively.

All the above studies had comparable results, but validity of these tests in the presence of inflammation was not shown. Hence in present study it was designed to look for the variation in sensitivity and specificity of iron parameters in the presence of inflammatory state.

In this study, newer parameters like CHr and Hypo% were evaluated in diagnosis of iron deficiency state in non dialysis CKD patients .Their validity was tested in the presence or absence of inflammation.

 Studies evaluating the combination of CHr with %hypo with iron studies parameters in predialysis chronic kidney disease patients are very few. In a study by Hesegawa et al (40) found similar predictive power various test parameters as in hemodialysis patients, but the validity of these parameter in the presence of inflammation has not been evaluated .

In similar studies by Tessitoire et al[50], in non dialysis patients, the sensitive of CHr varied from 58.67% to 84.5% and specificity of 78.88 to 88.67%.Validity of theses tests in the presence of inflammation has not been evaluated .

The base line mean MCV, CHr, TSAT, Serum ferritin, Reticulocyte count, were significantly lower in iron deficient in comparison to iron replete subjects. Patients with  inflammation had higher mean serum ferritin, low TIBC and Higher %Hypo when compared to absence of inflammation.

CONCLUSIONS

 Presence of inflammation interferes with the validity of various tests for the diagnosis. Routine parameters like, iron studies like serum ferritin and TSAT are still useful screening tests with good sensitivity.

Newer parameters like CHr and % Hypo, have variable sensitivity and specificity when used alone in CKD patients. The combination of CHr (<29) and %hypo(>2.5%) with iron parameters like serum ferritin or TSAT increases sensitivity and specificity in presence or absence of inflammation. Serum ferritin alone is a acute phase reactant and has poor specificity in the presence of inflammation. We recommend the tests for diagnosis (iron parameters, CHr, Hypo%) should be correlated with hs CRP(a marker of inflammation) before iron therapy.

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