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ORIGINAL ARTICLE
Year : 2011  |  Volume : 5  |  Issue : 1  |  Page : 6-11

Evaluation of the modified Alvarado score incorporating the C-reactive protein in the patients with suspected acute appendicitis


1 Department of Surgery, Sheri Kashmir Institute of Medical Sciences, Srinagar, India
2 Department of Surgery, SMHS Hospital, Srinagar, Jammu and Kashmir, India
3 Department of Medicine, Sheri Kashmir Institute of Medical Sciences, Srinagar, India

Date of Web Publication24-Aug-2011

Correspondence Address:
Sheikh Muzamil Shafi
Lal Bazar, Srinagar, Jammu and Kashmir
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0331-3131.84220

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   Abstract 

Background : Acute appendicitis is perhaps the most common surgically correctable cause of acute abdominal pain and its diagnosis remains difficult in many instances. Some of the signs and symptoms can be subtle to both the clinician and the patient and may not be present in all the instances. Arriving at the correct diagnosis is essential; however a delay in diagnosis may allow progression to perforation and significantly increase the morbidity and mortality.
Materials and Methods : This study was a prospective study and comprised 200 patients admitted with suspected acute appendicitis. The patients were selected unbiased from all age groups of either sex and were evaluated on the basis of predetermined proforma. Subsequent to hospital admission, the preoperative modified Alvarado score (MAS) was determined and C-reactive protein levels (CRP) were estimated. The results of the MAS and preoperative CRP levels were compared with the histopathology of the removed appendix.
Results : Among all the patients studied, 12, 52, and 136 patients had preoperative MAS of <5, 5-6, and 7-9 respectively. One hundred sixty six patients had CRP level raised. A total of 158 patients were histopathologically positive for apendicitis. The sensitivity and specificity of MAS in patients with a score of 5-6 were 58% and 13.5% respectively. In patients with a score of 7-9, MAS had sensitivity and specificity of 93% and 50% respectively. We found 93% sensitivity and 85% specificity of CRP for the diagnosis of acute appendicitis. When combined with CRP, the sensitivity and specificity of MAS in patients with score of 7-9 were raised to 98% and 54% respectively. Moreover, the sensitivity of MAS in patients with a score of 5-6 was raised significantly from 58% to 93%.
Conclusion : We concluded that MAS in combination with the CRP levels is very helpful in the diagnosis of acute appendicitis especially in patients with modified a Alvarado scores in the middle range, who are categorized as "equivocal" for appendicitis by the Alvarado score.

Keywords: Appendicitis, C-reactive protein, modified Alvarado score


How to cite this article:
Shafi SM, Malah MA, Malah HR, Reshi FA. Evaluation of the modified Alvarado score incorporating the C-reactive protein in the patients with suspected acute appendicitis. Ann Nigerian Med 2011;5:6-11

How to cite this URL:
Shafi SM, Malah MA, Malah HR, Reshi FA. Evaluation of the modified Alvarado score incorporating the C-reactive protein in the patients with suspected acute appendicitis. Ann Nigerian Med [serial online] 2011 [cited 2019 Sep 23];5:6-11. Available from: http://www.anmjournal.com/text.asp?2011/5/1/6/84220


   Introduction Top


The appendix is a structure without apparent function, yet it has been a frequent cause of morbidity and mortality. Methods of treating diseases of appendix have been developed primarily within the last 80 years, but knowledge of the disease goes back much further into the past. [1]

Appendicitis may occur for several reasons, such as an infection of the appendix, but the most important is the obstruction of the appendiceal lumen due to lymphoid hyperplasia, insipisated stools, etc., leading to bacterial overgrowth. The continued mucus secretion causes distention of the lumen leading to lymphatic and then venous obstruction, ensuing acute inflammatory response and ultimately to acute appendicitis, gangrene and perforation of the appendix. [2]

Among young male patients, the negative appendectomy rate is relatively low (5-22%), while for women of child-bearing age, the figure may be as high as 30-50%. In young children, the diagnosis may be wrong in 30-46% of the patients. The difficulty in diagnosing acute appendicitis in old age is reflected by the high incidence of perforation, 60-90% in many reports, rather than by a high rate of negative appendectomy. [3]

The usual picture of appendicitis is often not classical, leaving in many cases a diagnostic problem. In patients with questionable findings, the aggressive surgical approach has been "when in doubt, take it out," and the price paid was the frequent removal of normal appendices. The negative laparotomy was associated with definite morbidity but the mortality rate was minimal compared to the lethal potential of appendiceal perforation and peritonitis. [4]

To increase the diagnostic accuracy and to decrease the negative appendectomy rate, a variety of different approaches have been described, including the development of predictive scoring systems, [5] computer-aided diagnosis, [6] performance of diagnostic laparoscopy, [7],[8] ultrasonography, [9] computed tomography, [10] and magnetic resonance imaging. [11] The broad application of these studies in the preoperative diagnosis of appendicitis, however, remains controversial. [12]

Diagnostic scoring systems have been developed in an attempt to improve the diagnostic accuracy of acute appendicitis. The most prominent of those scores is that developed by Alvarado. [13]In his original paper, Alvarado recommended an operation for all patients with a score of 7 or more and observation for patients with scores of 5 or 6. [5] Subsequent prospective studies have suggested that the Alvarado score alone is inadequate as a diagnostic test. [14],[15]

The classic Alvarado score included left shift of neutrophil maturation (given a score of 1) yielding a total score of 10 but Kalan et al.,[16] omitted this parameter which is not routinely available in many laboratories, and produced a modified score. The modified Alvarado score has been widely accepted after it was successfully tested in different studies. [17]

An elevated level of C-reactive protein (CRP), an acute phase protein, is one of many downstream indicators of inflammation. In most, though not all diseases, the circulating value of CRP reflects ongoing inflammation and/or tissue damage much more accurately than do other laboratory parameters of the acute-phase response. The CRP concentration is thus a very useful but a nonspecific biochemical marker of inflammation, measurement of which contributes importantly to (a) screening for organic disease, (b) monitoring of the response to treatment of inflammation and infection, and (c) detection of intercurrent infection in immunocompromised individuals. [18]

The aim of this study was to determine the sensitivity and specificity of MAS separately and in combination with the CRP, to ensure preoperative diagnostic accuracy of appendicitis in patients with suspected acute appendicitis.


   Materials and Methods Top


This study was a prospective study and comprised 200 patients admitted in various surgical wards of our hospital. The patients were selected unbiased from all age groups of either sex and were evaluated on the basis of predetermined proforma.

Subsequent to hospital admission, preoperative MAS was determined and CRP was estimated. CRP of up to 10 μg/ml was considered upper limit of normal standard. Decision to operate was not affected by the preoperative modified Alvarado score or CRP levels.

Determination of the modified Alvarado score (MAS): MAS is based on three symptoms, three signs and one laboratory investigation, as shown in the [Table 1].
Table 1: Modified Alvarado score

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The estimated score was not revealed to the operating surgeon preoperatively, but postoperatively the calculated score of each patient was compared with the operative findings and the histopathology report.

Estimation of C-reactive protein (CRP):A rapid latex agglutination slide test was the standard for the qualitative and semi quantitative in vitro determination of CRP in the sample. It is based on the latex agglutination test. It was a qualitative test with the detection limit of approximately 6 mg/l.

For qualitative determination, the latex reagent was mixed thoroughly with the serum. Marked agglutination indicated a CRP concentration of more than 6 mg/l. A smooth homogenous milky suspension indicated a CRP concentration of less than 6 mg/l.

For semiquantitative determinations serum dilutions were prepared with the diluent provided with the kit according to the [Table 2].
Table 2: Serum dilutions and the CRP levels

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Each dilution was tested according to qualitative procedure described above until no further agglutination was observed. The CRP concentration was then estimated from the last dilution with visible agglutination:

CRP (mg/l) = Highest dilution with a positive reaction

X reagent sensitivity (6 mg/l)

Normal levels can be up to 6 mg/l in healthy adults. There are no significant differences in mean CRP values between adult males and nonpregnant females. [2],[7]


   Results Top


The study was conducted on 200 selected patients of all age groups and either sex with the age range of 4-65 years. The mean age of the patient was 23.30 years. There were 118 males and 82 females [Table 3].
Table 3: Sex distribution of the patients

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The difference in age (years) with regard to sex was statistically nonsignificant (P= 0.092).

The preoperative modified Alvarado score of all the patients included in the study was determined. On the basis of this scoring, there were 12 patients with score of <5, 52 with a score of 5-6, and 136 with a score of 7-9.

The appendix removed at surgery was subjected to histopathological examination. The histological diagnosis of acute appendicitis was made only if there was involvement of muscularis of the appendix. In all cases at least two transverse sections from the proximal half and one longitudinal section from the distal half were studied. On the basis of operative findings and histopathology report, patients were postoperatively diagnosed either as positive or negative for appendicitis.

Out of 42 cases negative for appendicitis, 19 had clear-cut other diagnosis. Rest of the patients had final diagnosis of nonspecific abdominal pain [Table 4].
Table 4: Showing diagnosis other than appendicitis in the selected patients

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Out of 118 male patients, 98 were positive for appendicitis. Similarly out of 82 female patients 60 were positive for appendicitis [Table 5].
Table 5: Showing results of histopathology in males and females

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Thus, sex distribution of cases with regard to appendicitis was statistically significant (P-value = 0.001).

Distribution of cases in different age groups with respect to histopathology of the removed appendix was as follows in [Table 6].
Table 6: Different age groups and histopathology of the removed appendix

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Statistically, a nonsignificant difference was observed (P= 0.855) in patients positive for appendicitis with regard to different age groups. Thus, any particular age group was not affected by appendicitis.

Modified Alvarado scoring in patients with positive histopathology for appendicitis was as follows; [Table 7]
Table 7: Modified Alvarado scoring in patients with positive histopathology

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A statistically highly significant difference was observed (P-value = 0.0001) in MAS with regard to appendicitis. Sensitivity of MAS was maximum (93 %) in patients with a score of 7-9.

The results of CRP and its sensitivity and specificity in our study are shown in the [Table 8].
Table 8: Results of preoperative C-reactive protein levels

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Statistically, a highly significant difference was observed in patients with raised CRP regarding appendicitis. Maximum sensitivity (93%) was observed in patients with raised CRP.

All the selected patients were subjected to appendectomy during the study period. On the basis of operative findings patients were divided into three groups;

Group A: Uninflamed appendix (42 patients): no apparent abnormality of the appendix, no signs of inflammation, no evidence of inflamed tip of appendix, no periappendicular fluid, no thickness of wall, or any fecolith within the appendix.

Group B: Inflamed but uncomplicated appendix (126 patients): thickened, edematous, grossly inflamed appendix with or without any fecolith, periappendicular fluid, or inflamed omentum.

Group C: Complicated appendix (32 patients): perforated appendix, appendicular lump, or abscess formation.

In group C, 30 patients had a score of 7-9; 2 patients had a score of 6. None of these patients had a score less than 6. All patients in this group had a raised C-reactive protein level.

Among 158 patients out of 200, who proved to be histopathologically positive for appendicitis, 63 had a score of 7-9. Among these patients, 62 had a raised CRP level; only one had a normal level. Fifteen patients had a score of 5-6; 14 of these patients had a raised CRP level, and 1 had a normal level. There was one patient with histopathology positive with a score of less than 5; this patient had a raised level of CRP [Table 9].
Table 9: Sensitivity and specificity of MAS incorporating CRP in patients with positive histopathology

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Thus, in patients with positive appendicitis with a preoperative score of 7-9, the sensitivity was raised from 93% to 98% when C-reactive protein was also positive. In patients with a score of 5-6, the sensitivity was raised significantly from 58% to 93%.

Correlation of MAS and CRP in patients with negative histopathology was as in the [Table 10].
Table 10: MAS and CRP in patients with negative histopathology

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   Discussion Top


Incorrectly diagnosing a patient with appendicitis, although not catastrophic, often subjects the patient to unnecessary laparotomy. [13] Removal of a noninflamed appendix also causes complications. Negative appendectomy is not a trivial problem. Flum and Koepsell assessed its impact in the United States--length of hospital stay, rate of complications, and mortality were all significantly higher in the negative appendectomy group. [19]

Laboratory studies can be helpful in the diagnosis of appendicitis, but no single test is definitive. A white blood cell count is perhaps the most useful test. Abdominal ultrasonography is a popular imaging modality for acute appendicitis having a sensitivity and specificity of 0.86 and 0.81 respectively. [13]

Because of the difficulty in diagnosing appendicitis, it is not uncommon for a normal appendix to be found at appendectomy. Sometimes referred to as misdiagnosis, this can occur more than 15% of the time, with considerably higher percentages in infants, the elderly and young women. Negative appendectomy is to be avoided when possible, due to the risk of surgical complications and the cost associated with the unnecessary surgery. [13]

In our study, all the patients were operated and decision to operate was not prejudiced by the preoperative modified Alvarado scoring or the level of CRP. On the basis of operative findings, patients were separated into uninflamed appendix, inflamed but uncomplicated appendix, and complicated appendix: groups A--C respectively.

On the basis of MAS, Gyomber D and Luck, grouped the patients as "unlikely" (score <5), "possible" (score 5-6) and "probable" appendicitis (score 7-9). Comparing histological findings to the modified Alvarado score, positive appendicitis was found in 38%, 73%, and 93% of the "unlikely," "possible," and "probable" groups respectively. [20] Similar results were found in our study.

Out of 42 patients with negative appendix, 12 had a raised value of CRP and 30 patients had CRP levels within normal range. In studies conducted by Asfar and Safar, [21] 13 out of 14 negative laparotomies had a CRP levels within the normal range.

In our study, CRP levels of all patients with complicated appendix were significantly raised preoperatively. Similar results were found in a study conducted by Gurleyik E, and Unalmişer S. In their study, the mean serum CRP value was 5 (0-12.6) mg/l in patients with normal appendix, 33.8 (5-85.1) mg/l in patients with nonperforated appendicitis, and 128.5 (79.2-230) mg/l in patients with perforated appendixes. [22] Eryilmaz R found in his study that although CRP increases with inflammation, it increases markedly after the occurrence of complication. [23]

Sensitivity and specificity of CRP in our study was 93.00%, and 85.00% respectively. The positive predictive value was 92.77%. Gurleyik and Unalmişer in their study calculated the sensitivity, specificity, and accuracy of serum CRP measurements as 93.5, 80, and 91%, respectively. [24]

In our study 30 of 42 patients with negative appendectomy had CRP levels within the normal range. If preoperative serum levels of CRP were to be believed, 30 negative laparotomies would have been avoided. In this study the negative exploration rate was 21%. In studies conducted by Erickson et al., negative appendectomy rate would have been fallen from 24% to 16% if preoperative serum values of CRP would have been followed. [25]

The sensitivity and specificity of MAS was raised when CRP levels were combined. In patients with a score of 7-9, the sensitivity was raised from 93% to 98% and specificity from 50% to 54%. In patients with a score of 5-6, the sensitivity was raised significantly from 58% to 93% and specificity from 13.5% to 23.5%.

In a previous study, Chan, et al. found that the Alvarado score was most accurate only at the two extremes of the score. [26] Our study also found it to be most accurate at the extreme of the scores. When CRP was also incorporated, we found that the sensitivity of the middle score (5-6) rose significantly from 58% to 93%.


   Conclusion Top


Our study concluded that diagnostic accuracy of acute appendicitis on the basis of clinical examination was less than 80%. MAS was sensitive, but with a relatively low specificity and alone does not contribute to the diagnosis of acute appendicitis in patients with equivocal clinical findings. CRP levels were found to be highly sensitive and specific for the diagnosis of acute appendicitis. The sensitivity and specificity was increased when CRP levels were combined with MAS. All the cases with complicated appendicitis were found to have high MAS with raised levels of CRP, reflecting increased accuracy of the combination in diagnosing acute appendicitis. When CRP levels were within the normal limits and the scores were low, acute appendicitis was unlikely. We found MAS to be most accurate at the extreme of the scores. When CRP was also incorporated in the patients with the middle score of 5-6 (equivocal for appendicitis), the sensitivity rose significantly from 58% to 93%.

Our study showed that in patients with high MAS and raised CRP levels, the probability of acute appendicitis was significantly increased with improved sensitivity and specificity. We believe that both MAS and CRP levels should be estimated in all patients who come to hospital with complaints of pain in the right iliac fossa. These are not costly to the patient, are noninvasive, and do not require any sophisticated equipments or technical expertise. Moreover, the results of these parameters can be obtained within no time making a surgeon to establish diagnosis immediately and thereby avoiding unwanted explorations and preventing complications (perforation, abscess).

 
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    Tables

  [Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7], [Table 8], [Table 9], [Table 10]


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