Helicobacter pylori-Associated Immune Thrombocytopenia: Diagnostic and Therapeutic Approach

Abstract

The relationship between immune thrombocytopenia (ITP) and Helicobacter pylori infection has largely been an unexplored entity. This review article aims at focusing on the role of H. pylori in secondary ITP. We also elucidated the importance of diagnostic workup and treatment of H. pylori in this article. The mechanisms of H. pylori-associated ITP have been covered in this article. The factors determining platelet response to H. pylori eradication therapy have been mentioned. It is extremely crucial to be aware that H. pylori is a major causative pathogen for new-onset ITP as well as chronic ITP. Upper gastrointestinal endoscopic biopsy is the best invasive method for the diagnosis of the same. Further studies need to be conducted across larger, more diverse groups to validate our observation that eradication of H. pylori could aid platelet recovery in ITP.

INTRODUCTION

Immune thrombocytopenia (ITP) is one of the causes of acquired thrombocytopenia due to immune-mediated destruction. There are several mechanisms behind immune-mediated destruction involving humoral and cellular autoimmunity. Autoantibodies have been found targeting glycoprotein (GP) IIb/IIIa. Primary ITP refers to ITP where an underlying trigger cannot be identified while secondary ITP is associated with several conditions such as systemic lupus erythematosus, leukemia, and infections such as HIV and hepatitis C. Helicobacter pylori is one such cause of ITP.[1] In cases of ITP secondary to H. pylori, eradication of H. pylori has got a significant impact on remission of ITP, enabling one to limit the use of immunosuppressant therapy. With this review, we have focused on the role of H. pylori in secondary ITP, diagnostic workup, and the impact of anti-H. pylori therapy in such cases.[2]

ITP is characterized by immune-mediated destruction of platelets. Depending on the duration since diagnosis, it can be divided into newly diagnosed (up to 3 months since diagnosis), persistent (3 to 12 months), and chronic ITP (more than 12 months since diagnosis).[3] The natural history of ITP is very heterogeneous. Age is one factor determining the same. The majority of adults have an acute onset and go on to develop chronic ITP compared to pediatric age group, where the majority undergo spontaneous resolution. Eighty percentage of children undergo spontaneous recovery within 6 months of onset, 5% within 6–12 months, and 15% go on to develop chronic ITP.[4,5,6,7]

PREVALENCE OF HELICOBACTER PYLORI AMONG IMMUNE THROMBOCYTOPENIA

The prevalence of H. pylori among patients with ITP varies with age and geographical area. Most studies were performed either among Italian subjects, where the general population showed a 50% infection rate of H. pylori across the years 1995–1997 or among Japanese individuals, where the prevalence of the same among the general population was found to be more than 70%.[8,9] While the general infection rates were high among the Italian and Japanese populations, a study conducted by Michel et al. to identify the infection’s prevalence specifically among 51 French-origin patients of ITP demonstrated a low prevalence of 29%, like that among the control population.[10,11] This study used serological methods to diagnose the presence of infection. Another study conducted by Michel et al. observed 74 patients of ITP of North American origin and found a similarly low prevalence of infection among them (22%); however, the method of diagnosis used was a breath test.[12] This low prevalence could also be compared to that among a geographically similar Caucasian healthy population.[13] In contrast, a Columbian study performed between 1998 and 2006 showed a very high infection prevalence (90.6%) among patients with ITP, significantly differing from the prevalence among the controls (43.8%).[14]

To summarize the various methods of diagnosis used, some of the above studies have used the 13C-urea breath test to detect H. pylori. In contrast, others relied on serological methods to diagnose and monitor the same infection. The varied results may be due to the different methods used to detect H. pylori and also due to variations in the ethnic origins of the populations enrolled in the studies. The use of serological methods as a diagnostic tool to identify H. pylori could be considered an inadequate choice by many, as such tests tend to remain positive for quite a while after treatment completion and are also not indicative of active H. pylori infection.[15] However, broadly, the systematic review did not show a difference in the prevalence between subjects having ITP with H. pylori infection and healthy population matched for age and geographical area.

ASSOCIATION BETWEEN HELICOBACTER PYLORI INFECTION AND IMMUNE THROMBOCYTOPENIA

H. pylori is a Gram-negative spiral bacterium known to cause gastrointestinal (GI) diseases such as chronic gastritis, peptic ulcer disease, and gastric cancer.[16]

H. pylori has also been found to cause extra-GI disorders such as cardiovascular, hematologic, and autoimmune diseases.[17] It was first observed in 1988 that there was an improvement in platelet count after infection by H. pylori was eradicated.[18,19] Since then, multiple studies have shown that with the eradication of H. pylori, there is a high possibility of resolution of ITP.[20]

The treatment regimen included standard triple therapy with a proton-pump inhibitor (PPI), clarithromycin, and either amoxicillin or metronidazole.[18] The first systematic review with the meta-analysis by Franchini et al. reviewed 17 studies in 2007 and reported an increase in platelet counts in patients with ITP after H. pylori eradication therapy.[21] Another systematic literature review that considered 1555 patients found an average response of 50.3% posteradication therapy (platelet count ≥30 × 109/L, and at minimum, doubling the basal count.[18] These findings indicate a clear link between H. pylori eradication and the improvement of platelet counts in patients with ITP. Based on these findings, the Maastricht V guidelines recommend the treatment of H. pylori eradication for chronic ITP.[22,23] The Korean Helicobacter Treatment Guidelines, 2013, recommend the eradication of H. pylori in ITP patients. However, the detection and eradication of H. pylori in patients with ITP is still controversial due to variances in the prevalence by population.[22,24]

MECHANISM OF HELICOBACTER PYLORI ASSOCIATED IMMUNE THROMBOCYTOPENIA

The association between H. pylori and ITP is known, but the mechanism or pathogenesis of ITP in a patient with H. pylori is under study, and there are few literary pieces regarding this subject.[25] Studies suggest that patients infected with CagA-positive strains had ITP.[26] Some studies suggest that the underlying mechanism is molecular mimicry, i.e., the antibodies which target the antigens present on H. pylori also act against specific GPs present on the surface of a platelet, while another study demonstrated that Anti-CagA antibodies cross-react specifically against a specific peptide expressed on the surface of the platelets only in patients of ITP [Figure 1].[26,27]

Figure 1.

Molecular mimicry resulting in antibodies formed against Helicobacter pylori attacking platelets

Another study on Italian subjects infected with H. pylori with ITP showed a higher prevalence of CagA gene of H. pylori than in the control group.[28] Studies suggest that the serum level of antibodies also recedes with the eradication of H. pylori in ITP patients. A study conducted by Takahashi et al. demonstrated that patient levels of antibodies against the CagA protein of the bacterium declined in three patients after eradication therapy.[29] Another study by Kodama et al. showed that a fall in the anti-CagA antibody titer after administering a H. pylori eradication regimen was more remarkable among treatment responders than nonresponders.[30] Such observations could lead us to consider the possible role of Anti-CagA antibody titres as a potential clinical biomarker to help decide the requirement of bacterial eradication therapy among ITP patients.[27]

Another possible antigen that has been studied is Lewis (Le) antigen. In some subjects, it was observed that there is a possible role of these antigens initiating the platelet destruction, but eventually, with time the thrombocytopenia becomes refractory to the eradication of H. pylori.[31] This pattern of response to treatment is similar to that employed by the bacterium in the pathogenesis and progression of MALTomas, where early treatment with eradication therapy may show benefits before the development of resistant forms of the disease due to novel mutations produced by H. pylori.[26]

It has been observed that some strains of the bacterium bind to von Willebrand factor on the platelets and bring about platelet aggregation when in the presence of the corresponding anti-H. pylori antibodies [Figure 2]. This aggregation is caused by an interaction between GP Ib and Fc Receptor subtype IIa. H. pylori infection also decreases the levels of the inhibitor of Fc Gamma receptor IIB on monocytes. It thus causes an increase in Fc Gamma receptor levels, leading to these cells’ clonal expansion. Therefore, a monocyte-predominant phenotype is seen to develop, which is a highly phagocytic state.[32]

Figure 2.

Von willebrand factor mediated platelet aggregation by Helicobacter pylori

A study by Veneri et al. demonstrated the role of genetic factors in the correlation between ITP and H. pylori infection.[33] It was observed that patients of ITP infected with H. pylori had associated higher frequencies of human leukocyte antigen (HLA) subtypes DRB1 * 11, DRB1 * 14 and DQB1 * 03 and a lower frequency of occurrence of DRB1 * 03. In addition, it was seen that a high frequency of DQB1 * 03 could correlate with better platelet response to bacterial eradication therapies.[18]

TESTING FOR HELICOBACTER PYLORI

There are several invasive and noninvasive tests available at present. Invasive methods include biopsy urease testing and Giemsa staining of biopsy specimens. In biopsy urease testing, gastric biopsy specimen is placed in a medium containing urea and pH reagent. Urease of H. pylori splits urea into ammonia resulting in alkaline pH and resultant color change. Sensitivity and specificity are 90% and 95%, respectively.[34] Special stains such as Giemsa stain can be added to improve detection rates, resulting in a sensitivity of 95% and specificity of 98%.[35] Some noninvasive diagnostic modalities are stool antigen assay, serological test, and urea breath test. Stool antigen testing is a cost-effective method. It can be affected by the use of bismuth compounds, antibiotics, and PPIs. The patient should be off antibiotics for 4 weeks and PPI for 1 to 2 weeks before testing.[34]

The serology test involves the enzyme-linked immunosorbent assay for immunoglobulin G detection, but it has limited sensitivity (85%) and specificity (79%). It cannot distinguish between active and past infection. Following serological testing, it may be required to perform stool or breath to confirm.[35] In urea breath testing, carbon-labeled urea is administered orally, and H. pylori causes hydrolysis of urea to ammonia and carbon dioxide. Carbon dioxide containing labeled carbon is detected on breath as a marker of H. pylori infection. It has a sensitivity nearing 95% and a specificity of 95%–100%.[36] False-negative results can occur among those taking PPIs, bismuth, and antibiotics.[37]

HELICOBACTER PYLORI ERADICATION THERAPY

Triple and quadruple therapy is available presently for H. pylori eradication. Triple therapy involves a PPI and two antibiotics (Clarithromycin and Amoxicillin/Metronidazole).[38] Quadruple therapy includes bismuth in addition to PPI and antibiotics (tetracycline and metronidazole). The duration of therapy is 14 days.[39]

Up to 20% failure rates can be noted with the first-line therapy. Confirmation of eradication is required after the completion of a treatment course.[40] H. pylori eradication in ITP has been shown to help in complete or partial remission of ITP, and remission has been found to be sustained in significant number of cases, although few studies have shown inadequate response to H. pylori eradication [Table 1]. H. pylori eradication in ITP would thus lead to better cure rates. It is a potential long-term treatment strategy with lesser need for other agents such as steroids, and thrombopoietin receptor agonists which are associated with their own set of adverse effects and costly in the long run.

Table 1.

List of studies comparing good vs bad response of ITP to H.pylori therapy

Authors	Year of study	n	Study participants and intervention	Study findings
Studies showing good response of ITP to H. pylori therapy
Gasbarrini et al. (Italy)[19]	1998	18	11 adult participants with ITP and H. pylori infection Amoxicillin (1000 mg twice daily), clarithromycin (250 mg three times daily), and pantoprazole (40 mg twice daily) was given for 7 days	Eradication of H. pylori was achieved in 8 patients These patients demonstrated a significant increase in platelet count after 2 and 4 months of therapy (P<0.05) 6 out of these 8 patients had disappearance of autoantibodies against platelets (P<0.003)
Veneri et al. (Italy)[33]	2005	52	34 adult participants with ITP and H. pylori infection Amoxicillin (1000 mg twice daily) and clarithromycin (250 mg thrice daily) for 7 days, pantoprazole (20 mg twice daily) for 14 days	Bacterium eradication was accompanied by a long-term platelet response in 17 (53.1%) The mean platelet count before and after eradication treatment was 57.1±23.3×109/L and 122.3±33.2×109/L, respectively (P<0.001) Among the 32 patients who eradicated H. pylori, 18 patients (56.2%) obtained a complete (8 patients) or partial (10 patients) response
Stasi et al. (Italy/UK)[41]	2005	137	H. pylori infection was detected in 64 patients (47%) Eradication therapy was successfully administered to 52 patients The regimen for H. pylori eradication consisted of amoxicillin (1000 mg twice daily), clarithromycin (500 mg twice daily), and omeprazole (20 mg twice daily) for 7 days	A major platelet response was obtained in 14 (27%) of the 52 patients, and a partial response in 3 patients (6%), for an overall response rate of 33% Responses were sustained in 11 patients. 6 patients experienced a relapse Successful re-treatment with eradication therapy resulted in a new sustained platelet response
Fujimura et al. (Japan)[42]	2005	435	300 patients were diagnosed with H. pylori positive (positive rate, 69%) Lansoprazole 60 mg/day, clarithromycin 400 mg/day, and amoxicillin 1500 mg/day, administered together twice a day for 7 days	A significant increase in platelet count at the final observation was found in 101 (63%) of the 161 cases in which eradication of H. pylori was successful and in 15 (33%) of the 46 cases in which eradication was not successful (P<0.005) At 12 months posteradication, 28 (23%) of the cases were in complete remission while 51 (42%) of the cases were in partial remission
Kodama et al. (Japan)[30]	2007	116	H. pylori infection was found in 67 (58%) of the 116 patients with ITP 52 infected patients received eradication therapy The H. pylori eradication therapy regime consisted of amoxicillin (1500 mg twice daily), clarithromycin (400 mg) twice daily), and lansoprazole (60 mg twice daily) for 7 days	The bacterium was successfully eradicated in 44 of these 52 patients (84.6%) Complete remission of ITP was achieved in 8 (18.1%) of the 44 patients, and partial remission was achieved in 19 of the 44 patients (43.2%), for an overall response rate of 61.4%
Hwang et al. (Korea)[43]	2016	102	The prevalence of H. pylori infection was 41.1% (42/102) Rabeprazole 20 mg twice a day, amoxicillin 1000 mg twice a day, and clarithromycin 500 mg twice a day was given for 1 week to eradicate H. pylori	The platelet counts of the H. pylori-positive and eradicated group were significantly increased 6 months after eradication therapy compared to those of the H. pylori-positive and- noneradicated group and the H. pylori-negative group (43.2±29.1–155.3±68.7×103/μL vs. 42.5±28.1–79.8±59.7×103/μL vs. 43.1±28.9–81.2±62.2×103/μL; P=0.041)
Aljarad et al. (Syria)[44]	2018	50	H. pylori infection detected in 36 patients (72%) Omeprazole 40 mg once daily, amoxicillin 1000 mg twice daily, clarithromycin 500 mg twice daily given for 14 days	10 patients (27.77%) achieved complete remission, and 18 patients (50%) achieved partial response
Studies showing poor response of ITP to H. pylori therapy
Jarque et al. (Spain)[45]	2001	56	32 adult participants with ITP and H. pylori infection Omeprazole 20 mg twice daily, claritromycin 500 mg twice daily and amoxycillin 1 g twice daily was given for 7–10 days	Eradication of H. pylori was achieved in 23 out of 32 assessable patients Platelet increment (>30×109/L) was noted in 3 patients out of the 23 who responded to eradication therapy
Ahn et al. (USA)[46]	2006	15	15 ITP patients diagnosed with H. pylori infection were enrolled in the study Lansoprazole 30 mg, amoxicillin 500 mg, clarithromycin 500 mg two times a day was administered for 2 weeks	Two out of 15 patients showed improvement in platelet counts after 6 months Overall, certain platelet response rate was 6.7% (1/15) since 1 patient had ITP attributable to a drug

ITP: Immune thrombocytopenia, H. pylori: Helicobacter pylori

FACTORS DETERMINING PLATELET RESPONSE TO HELICOBACTER PYLORI ERADICATION THERAPY

Several factors have been identified to influence the response to H. pylori eradication therapy in patients with ITP. A favorable response to the therapy has been associated with certain characteristics. First, patients with a shorter duration of ITP tend to exhibit better responses to the treatment, suggesting that early intervention may be beneficial.[30,41,42] In addition, age at the time of ITP diagnosis plays a role, with patients under the age of 65 years demonstrating a higher likelihood of responding positively.[41] Moreover, a higher baseline platelet count has been linked to improved response rates, implying that patients with relatively higher platelet levels may have a better chance of achieving remission.[41] Prior corticosteroid therapy and concomitant steroid use have also been identified as potential factors that could negatively impact treatment outcomes, highlighting the importance of considering treatment history.[47,48,49] Moreover, genetic factors have also emerged as the determinants of response to H. pylori eradication therapy in ITP. The presence of the HLA-DQB1 * 03 haplotype, as well as specific single nucleotide polymorphisms within the genes for tumor necrosis factor-β and an inhibitory Fcγ receptor IIB, have been associated with differential treatment responses.[33,48,50] Understanding these factors can aid in predicting treatment outcomes and optimizing therapeutic strategies for patients with ITP. It is worthnoting that a study from Italy reported that ITP patients with antibodies to CagA were more likely to respond to eradication therapy than patients without these antibodies, although a study conducted in Japan failed to confirm this observation. However, it should be recognized that CagA-positive strains are more common in Japan than in Italy, which could account for the conflicting data.[47,51] Further research is needed to elucidate the role of CagA antibodies in treatment response.

EFFECT OF HELICOBACTER PYLORI ERADICATION AGENTS IN UNINFECTED IMMUNE THROMBOCYTOPENIA PATIENTS

The hypothesis of an independent effect of H. pylori treatment in noninfected ITP patients had been proposed, suggesting that the eradication of H. pylori could improve platelet autoreactivity and stimulate platelet responses. This hypothesis is supported by the several factors. First, macrolide antibiotics, including clarithromycin, which are universally included in H. pylori eradication regimens, possess anti-inflammatory properties that may enhance platelet function by blocking the production of proinflammatory cytokines.[52] In addition, antimicrobials used for H. pylori treatment have the potential to eradicate other commensal bacteria that could stimulate cross-reactive platelet antibodies. To investigate the specific impact of H. pylori eradication, treated H. pylori-negative patients were used as controls in a systematic review which unequivocally confirmed that the effect of H. pylori treatment is indeed attributable to the eradication of the bacteria rather than the treatment itself.[21,53] Platelet responses were observed only rarely in uninfected patients and in patients whose infection could not be eradicated, occurring at a rate similar to that of spontaneous remissions expected in this patient population. Moreover, other studies which enrolled uninfected patients who received eradication therapy, consistently reported no platelet response. This finding strongly suggests that the platelet response may be influenced by the eradication of H. pylori rather than the eradication therapy alone. These findings challenge the notion that noninfected ITP patients may respond to treatment independently of H. pylori eradication. The data indicate that the presence of H. pylori and its subsequent eradication play a critical role in determining platelet response rates.

CONCLUSION

It can be concluded that H. pylori is an important cause of secondary ITP. Therefore, it is of extreme importance to test for H. pylori in all newly detected cases of ITP as well as chronic ITP. This can lead to better response that is sustained with minimal use of other standard regimens of ITP. Ideal testing method is invasive one involving biopsy urease testing. However, there are scenarios such as severe thrombocytopenia and patient not consenting for invasive testing where it may not be possible to perform endoscopy. In such conditions, noninvasive testing methods can be used.

More studies would be required to strengthen the evidence for H. pylori eradication in ITP and formulate diagnostic and therapeutic guidelines regarding the same.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.