Systematic review with meta-analysis: limited benefits from early colonoscopy in acute lower gastrointestinal bleeding

Problematic meta-analyses: Bayesian and frequentist perspectives on combining randomized controlled trials and non-randomized studies

PURPOSE

In the literature, the propriety of the meta-analytic treatment-effect produced by combining randomized controlled trials (RCT) and non-randomized studies (NRS) is questioned, given the inherent confounding in NRS that may bias the meta-analysis. The current study compared an implicitly principled pooled Bayesian meta-analytic treatment-effect with that of frequentist pooling of RCT and NRS to determine how well each approach handled the NRS bias.

MATERIALS & METHODS

Binary outcome Critical-Care meta-analyses, reflecting the importance of such outcomes in Critical-Care practice, combining RCT and NRS were identified electronically. Bayesian pooled treatment-effect and 95% credible-intervals (BCrI), posterior model probabilities indicating model plausibility and Bayes-factors (BF) were estimated using an informative heavy-tailed heterogeneity prior (half-Cauchy). Preference for pooling of RCT and NRS was indicated for Bayes-factors > 3 or < 0.333 for the converse. All pooled frequentist treatment-effects and 95% confidence intervals (FCI) were re-estimated using the popular DerSimonian-Laird (DSL) random effects model.

RESULTS

Fifty meta-analyses were identified (2009-2021), reporting pooled estimates in 44; 29 were pharmaceutical-therapeutic and 21 were non-pharmaceutical therapeutic. Re-computed pooled DSL FCI excluded the null (OR or RR = 1) in 86% (43/50). In 18 meta-analyses there was an agreement between FCI and BCrI in excluding the null. In 23 meta-analyses where FCI excluded the null, BCrI embraced the null. BF supported a pooled model in 27 meta-analyses and separate models in 4. The highest density of the posterior model probabilities for 0.333 < Bayes factor < 1 was 0.8.

CONCLUSIONS

In the current meta-analytic cohort, an integrated and multifaceted Bayesian approach gave support to including NRS in a pooled-estimate model. Conversely, caution should attend the reporting of naïve frequentist pooled, RCT and NRS, meta-analytic treatment effects.

Review article: Advances in the management of lower gastrointestinal bleeding

BACKGROUND

Lower gastrointestinal bleeding (LGIB) is a common emergency with substantial associated morbidity and mortality. Elective colonoscopy plays an essential role in management, with an even more important role for radiology in the acute setting. Recent advances in the management of patients with LGIB warrant review as the management has recently evolved.

AIMS

To provide a comprehensive and updated overview of advances in the approach to patients with LGIB METHODS: We performed a comprehensive literature search to examine the current data for this narrative review supplemented by expert opinion.

RESULTS

The incidence of LGIB is increasing worldwide, partly related to an ageing population and the increasing use of antithrombotics. Diverticulosis continues to be the most common aetiology of LGIB. Pre-endoscopic risk stratification tools, especially the Oakland score, can aid appropriate patient triage. Adequate resuscitation continues to form the basis of management, while appropriate management of antithrombotics is crucial to balance the risk of worsening bleeding against increased cardiovascular risk. Radiological imaging plays an essential role in the diagnosis and treatment of acute LGIB, especially among unstable patients. Colonoscopy remains the gold-standard test for the elective management of stable patients.

CONCLUSIONS

The management of LGIB has evolved significantly in recent years, with a shift towards radiological interventions for unstable patients while reserving elective colonoscopy for stable patients. A multidisciplinary approach is essential to optimise the outcomes of patients with LGIB.

Weekend Effect on Clinical Outcomes of Acute Lower Gastrointestinal Bleeding: A Large Multicenter Cohort Study in Japan

INTRODUCTION

Weekend admissions showed increased mortality in several medical conditions. This study aimed to examine the weekend effect on acute lower gastrointestinal bleeding (ALGIB) and its mortality and other outcomes.

METHODS

This retrospective cohort study (CODE BLUE-J Study) was conducted at 49 Japanese hospitals between January 2010 and December 2019. In total, 8,120 outpatients with acute hematochezia were enrolled and divided into weekend admissions and weekday admissions groups. Multiple imputation (MI) was used to handle missing values, followed by propensity score matching (PSM) to compare outcomes. The primary outcome was mortality; the secondary outcomes were rebleeding, length of stay (LOS), blood transfusion, thromboembolism, endoscopic treatment, the need for interventional radiology, and the need for surgery. Colonoscopy and computed tomography (CT) management were also evaluated.

RESULTS

Before PSM, there was no significant difference in mortality (1.3% vs. 0.9%, p = 0.133) between weekend and weekday admissions. After PSM with MI, 1,976 cases were matched for each admission. Mortality was not significantly different for weekend admissions compared with weekday admissions (odds ratio [OR] 1.437, 95% confidence interval [CI] 0.785-2.630; p = 0.340). No significant difference was found with other secondary outcomes in weekend admissions except for blood transfusion (OR 1.239, 95% CI 1.084-1.417; p = 0.006). Weekend admission had a negative effect on early colonoscopy (OR 0.536, 95% CI 0.471-0.609; p < 0.001). Meanwhile, urgent CT remained significantly higher in weekend admissions (OR 1.466, 95% CI 1.295-1.660; p < 0.001).

CONCLUSION

Weekend admissions decrease early colonoscopy and increase urgent CT but do not affect mortality or other outcomes except transfusion.

LONG-HOSP Score: A Novel Predictive Score for Length of Hospital Stay in Acute Lower Gastrointestinal Bleeding - A Multicenter Nationwide Study

INTRODUCTION

Length of stay (LOS) in hospital affects cost, patient quality of life, and hospital management; however, existing gastrointestinal bleeding models applicable at hospital admission have not focused on LOS. We aimed to construct a predictive model for LOS in acute lower gastrointestinal bleeding (ALGIB).

METHODS

We retrospectively analyzed the records of 8,547 patients emergently hospitalized for ALGIB at 49 hospitals (the CODE BLUE-J Study). A predictive model for prolonged hospital stay was developed using the baseline characteristics of 7,107 patients and externally validated in 1,440 patients. Furthermore, a multivariate analysis assessed the impact of additional variables during hospitalization on LOS.

RESULTS

Focusing on baseline characteristics, a predictive model for prolonged hospital stay was developed, the LONG-HOSP score, which consisted of low body mass index, laboratory data, old age, nondrinker status, nonsteroidal anti-inflammatory drug use, facility with ≥800 beds, heart rate, oral antithrombotic agent use, symptoms, systolic blood pressure, performance status, and past medical history. The score showed relatively high performance in predicting prolonged hospital stay and high hospitalization costs (area under the curve: 0.70 and 0.73 for derivation, respectively, and 0.66 and 0.71 for external validation, respectively). Next, we focused on in-hospital management. Diagnosis of colitis or colorectal cancer, rebleeding, and the need for blood transfusion, interventional radiology, and surgery prolonged LOS, regardless of the LONG-HOSP score. By contrast, early colonoscopy and endoscopic treatment shortened LOS.

CONCLUSIONS

At hospital admission for ALGIB, our novel predictive model stratified patients by their risk of prolonged hospital stay. During hospitalization, early colonoscopy and endoscopic treatment shortened LOS.

Management of Patients With Acute Lower Gastrointestinal Bleeding: An Updated ACG Guideline

Acute lower gastrointestinal bleeding (LGIB) is a common reason for hospitalization in the United States and is associated with significant utilization of hospital resources, as well as considerable morbidity and mortality. These revised guidelines implement the Grading of Recommendations, Assessment, Development, and Evaluation methodology to propose recommendations for the use of risk stratification tools, thresholds for red blood cell transfusion, reversal agents for patients on anticoagulants, diagnostic testing including colonoscopy and computed tomography angiography (CTA), endoscopic therapeutic options, and management of antithrombotic medications after hospital discharge. Important changes since the previous iteration of this guideline include recommendations for the use of risk stratification tools to identify patients with LGIB at low risk of a hospital-based intervention, the role for reversal agents in patients with life-threatening LGIB on vitamin K antagonists and direct oral anticoagulants, the increasing role for CTA in patients with severe LGIB, and the management of patients who have a positive CTA. We recommend that most patients requiring inpatient colonoscopy undergo a nonurgent colonoscopy because performing an urgent colonoscopy within 24 hours of presentation has not been shown to improve important clinical outcomes such as rebleeding. Finally, we provide updated recommendations regarding resumption of antiplatelet and anticoagulant medications after cessation of LGIB.

Timing of colonoscopy in acute lower GI bleeding: a multicenter retrospective cohort study

BACKGROUND AND AIMS

We aimed to determine the optimal timing of colonoscopy and factors that benefit patients who undergo early colonoscopy for acute lower GI bleeding.

METHODS

We identified 10,342 patients with acute hematochezia (CODE BLUE-J study) admitted to 49 hospitals in Japan. Of these, 6270 patients who underwent a colonoscopy within 120 hours were included in this study. The inverse probability of treatment weighting method was used to adjust for baseline characteristics among early (≤24 hours, n = 4133), elective (24-48 hours, n = 1137), and late (48-120 hours, n = 1000) colonoscopy. The average treatment effect was evaluated for outcomes. The primary outcome was 30-day rebleeding rate.

RESULTS

The early group had a significantly higher rate of stigmata of recent hemorrhage (SRH) identification and a shorter length of stay than the elective and late groups. However, the 30-day rebleeding rate was significantly higher in the early group than in the elective and late groups. Interventional radiology (IVR) or surgery requirement and 30-day mortality did not significantly differ among groups. The interaction with heterogeneity of effects was observed between early and late colonoscopy and shock index (shock index <1, odds ratio [OR], 2.097; shock index ≥1, OR, 1.095; P for interaction = .038) and performance status (0-2, OR, 2.481; ≥3, OR, .458; P for interaction = .022) for 30-day rebleeding. Early colonoscopy had a significantly lower IVR or surgery requirement in the shock index ≥1 cohort (OR, .267; 95% confidence interval, .099-.721) compared with late colonoscopy.

CONCLUSIONS

Early colonoscopy increased the rate of SRH identification and shortened the length of stay but involved an increased risk of rebleeding and did not improve mortality and IVR or surgery requirement. Early colonoscopy particularly benefited patients with a shock index ≥1 or performance status ≥3 at presentation.

Clinical Characteristics and Outcomes of Hospital-Acquired Lower Gastrointestinal Bleeding: A Single Centre Retrospective Cohort Study

Background Lower gastrointestinal bleeding (LGIB) is common in inpatient and outpatient settings; however, there are limited studies on the clinical characteristics and patient outcomes of those with hospital-acquired LGIB. Methods We performed a retrospective cohort study of patients with hospital-acquired LGIB who underwent colonoscopy during hospitalization between January 2017 and December 2021. We described the clinical characteristics, etiology, and clinical outcomes of patients stratified as those undergoing colonoscopy within 24 hours from haematochezia onset (early colonoscopy group) or after 24 hours from onset (late colonoscopy group). We used multivariable logistic regression to identify factors associated with endoscopic intervention in the early and late colonoscopy groups. Results Of the 272 patients included, the median age was 79 years (interquartile range: 72-85 years), 153 (56%) were bedridden, and 172 (63%) had hypoalbuminemia. The most frequent etiology was rectal ulcer (101 cases, 37%), whereas 7 (2.6%) had diverticular bleeding. The endoscopic intervention was performed on 16.7% and 7.9% of early and late colonoscopy patients. There were more patients with both non-severe and severe rebleeding in the early colonoscopy group (16% and 12%, respectively) than in the late colonoscopy group (11% and 6.5%, respectively). Colonoscopy-on-worktime was the only factor independently associated with a higher occurrence of endoscopic intervention. Conclusions In our sample, very old patients with hospital-acquired LGIB required endoscopy mainly due to rectal ulcers. Further studies will be necessary to investigate the differences between community-acquired LGIB and hospital-acquired LGIB and the optimal timing of colonoscopy for these patients.

How to manage lower gastrointestinal bleeding in 2022?

Lower gastrointestinal bleeding (LGIB), originating mainly in the colon, rectum and anus, occurs most often in older patients (7th decade) with co-morbidity, half of whom have coagulation abnormalities due to anti-coagulant or anti-aggregant therapy. In three cases out of four, bleeding regresses spontaneously but can recur in up to one third of patients. The main causes are diverticular disease, vascular disorders (hemorrhoids, angiodysplasia) and colitis. Ten to 15% of patients present in hypovolemic shock. The main problem is to determine the precise location and etiology of bleeding. First-line steps include correction of hemodynamics, correction of coagulation disorders and transfusion, as necessary. Rectal digital examination allows differentiation between melena and hematochezia. In patients with severe LGIB, upper endoscopy can eliminate upper gastro-intestinal bleeding (UGIB). Computerized tomography (CT) angiography can pinpoint the source. If contrast material extravasates, the therapeutic strategy depends on the cause of bleeding and the general status of the patient: therapeutic colonoscopy, arterial embolization and/or surgery. In the absence of severity criteria (Oakland score≤10), ambulatory colonoscopy should be performed within 14 days. Discontinuation of anticoagulant and/or antiplatet therapy should be discussed case by case according to the original indications.

Early Colonoscopy Does Not Affect 30-Day Readmission After Lower GI Bleeding: Insights from a Nationwide Analysis

INTRODUCTION

Lower gastrointestinal bleeding (LGIB) is one of the most common indications for hospital admission. The current standard of care for patients admitted with LGIB includes colonoscopy. The aims of this study are to define the rate of readmission in patients with LGIB and to determine whether early colonoscopy within the first 24 h after admission impacts the rate of readmission in these patients.

METHODS

We performed a retrospective cohort study on data obtained from the Nationwide Readmission Database and identified patients admitted with lower GI bleed using ICD-10 codes. The primary outcome was 30-day all-cause readmission, and one of our secondary outcomes was the impact of early colonoscopy on 30-day readmission.

RESULTS

We analyzed data from 35,790,513 patients who were admitted for LGIB in 2017. A total of 16.4% of these patients were readmitted within 30 days of discharge, with diverticular bleeding most common diagnosis for readmission. Overall, in-hospital mortality was 1.18% for index admission and 4.44% for readmission. Early colonoscopy did not impact the rate of readmission within 30 days of discharge.

CONCLUSION

LGIB remains a commonly encountered in clinical practice with a high readmission rate. Mortality is significantly higher during readmission compared to index admission. Early colonoscopy did not impact the 30-day readmission rate.

Optimal candidates for early colonoscopy in the management of acute lower gastrointestinal bleeding

BACKGROUND AND AIM

Early colonoscopy has not shown any advantages over elective colonoscopy in reducing the risk of early rebleeding (≤ 30 days) after acute lower gastrointestinal bleeding (ALGIB). Considering the heterogeneity among patients with ALGIB, we sought to evaluate appropriate candidates for early colonoscopy.

METHODS

A total of 592 patients with ALGIB were enrolled, and the clinical outcomes of early colonoscopy were investigated. Thereafter, the participants were divided into two groups: the recent bleeding group (n = 445), with hematochezia 0-6 h before hospital arrival, and non-recent bleeding group (n = 147). The clinical outcomes yielded by early colonoscopy were assessed in each group.

RESULTS

The multivariate analysis including the entire population revealed that early colonoscopy (< 24 h) did not reduce the risk of early rebleeding (adjusted odds ratio [AOR], 0.88; 95% confidence interval [CI], 0.55-1.39). However, in the subgroup analysis, early colonoscopy independently reduced the risk of early rebleeding in the recent bleeding group (AOR, 0.56; 95% CI, 0.33-0.94). Moreover, a reduction in the need for radiological or surgical intervention (AOR, 0.34), transfusion (AOR, 0.62), and prolonged hospitalization (AOR, 0.42), as well as improvement in diagnostic yield (AOR, 1.78) and endoscopic treatment rates (AOR, 1.66), were observed. Early colonoscopy did not improve the outcomes of the non-recent bleeding group.

CONCLUSIONS

Early colonoscopy is not required for all patients with ALGIB. However, it may be suitable for those with hematochezia 0-6 h before hospital arrival, as it reduces early rebleeding and improves clinical outcomes.

Lower Gastrointestinal Bleeding

Lower gastrointestinal (LGI) bleeding indicates bleeding from colon or anorectum. Typically, patients with LGI bleeding present with bright red blood per rectum or hematochezia, although rarely they can present with melena as well. Alternatively, LGI bleeding is also defined as bleeding from a source within potential reach of a colonoscope, that is, colon and terminal ileum. LGI bleedings have more favorable outcomes than upper GI (UGI) bleeding and less common than UGI bleeding. Any patient presenting with GI bleeding should undergo a detailed history and physical examination for clues that may suggest source and possible etiology. Colonoscopy remains the most widely used and preferred instrument of choice for both diagnosis and therapy. This review will discuss in brief the causes, triaging, and role of colonoscopy in the management of LGI bleeding.

Acute Upper Non-variceal and Lower Gastrointestinal Bleeding

Acute gastrointestinal (GI) bleeding is a common surgical emergency requiring hospital admission and associated with high morbidity and mortality. Appropriate decision-making is essential to make a prompt diagnosis, accurate risk assessment, and proper resuscitation of patients with gastrointestinal bleeding. Despite multiple randomized trials and meta-analyses, there is still controversy on various management issues like appropriate risk stratification, the timing of endoscopy, choosing an appropriate endoscopic, and radiological intervention in these groups of patients. As the usage of nonsteroidal anti-inflammatory drugs, antiplatelet, and antithrombotic agents is common in patients with gastrointestinal bleeding, the physician is challenged with proper management of these drugs. The present review summarizes the current strategies for risk stratification, localization of bleeding source, endoscopic and radiological intervention in patients with acute nonvariceal upper GI, middle GI, and lower GI bleeding.

Endoscopic direct clipping versus indirect clipping for colonic diverticular bleeding: A large multicenter cohort study

BACKGROUND

Direct and indirect clipping treatments are used worldwide to treat colonic diverticular bleeding (CDB), but their effectiveness has not been examined in multicenter studies with more than 100 cases.

OBJECTIVE

We sought to determine the short- and long-term effectiveness of direct versus indirect clipping for CDB in a nationwide cohort.

METHODS

We studied 1041 patients with CDB who underwent direct clipping (n = 360) or indirect clipping (n = 681) at 49 hospitals across Japan (CODE BLUE-J Study).

RESULTS

Multivariate analysis adjusted for age, sex, and important confounding factors revealed that, compared with indirect clipping, direct clipping was independently associated with reduced risk of early rebleeding (<30 days; adjusted odds ratio [AOR] 0.592, p = 0.002), late rebleeding (<1 year; AOR 0.707, p = 0.018), and blood transfusion requirement (AOR 0.741, p = 0.047). No significant difference in initial hemostasis rates was observed between the two groups. Propensity-score matching to balance baseline characteristics also showed significant reductions in the early and late rebleeding rates with direct clipping. In subgroup analysis, direct clipping was associated with significantly lower rates of early and late rebleeding and blood transfusion need in cases of stigmata of recent hemorrhage with non-active bleeding on colonoscopy, right-sided diverticula, and early colonoscopy, but not with active bleeding on colonoscopy, left-sided diverticula, or elective colonoscopy.

CONCLUSIONS

Our large nationwide study highlights the use of direct clipping for CDB treatment whenever possible. Differences in bleeding pattern and colonic location can also be considered when deciding which clipping options to use.

Diagnosis and management of acute lower gastrointestinal bleeding: European Society of Gastrointestinal Endoscopy (ESGE) Guideline

1: ESGE recommends that the initial assessment of patients presenting with acute lower gastrointestinal bleeding should include: a history of co-morbidities and medications that promote bleeding; hemodynamic parameters; physical examination (including digital rectal examination); and laboratory markers. A risk score can be used to aid, but should not replace, clinician judgment.Strong recommendation, low quality evidence. 2 : ESGE recommends that, in patients presenting with a self-limited bleed and no adverse clinical features, an Oakland score of ≤ 8 points can be used to guide the clinician decision to discharge the patient for outpatient investigation.Strong recommendation, moderate quality evidence. 3 : ESGE recommends, in hemodynamically stable patients with acute lower gastrointestinal bleeding and no history of cardiovascular disease, a restrictive red blood cell transfusion strategy, with a hemoglobin threshold of ≤ 7 g/dL prompting red blood cell transfusion. A post-transfusion target hemoglobin concentration of 7-9 g/dL is desirable.Strong recommendation, low quality evidence. 4 : ESGE recommends, in hemodynamically stable patients with acute lower gastrointestinal bleeding and a history of acute or chronic cardiovascular disease, a more liberal red blood cell transfusion strategy, with a hemoglobin threshold of ≤ 8 g/dL prompting red blood cell transfusion. A post-transfusion target hemoglobin concentration of ≥ 10 g/dL is desirable.Strong recommendation, low quality evidence. 5: ESGE recommends that, in patients with major acute lower gastrointestinal bleeding, colonoscopy should be performed sometime during their hospital stay because there is no high quality evidence that early colonoscopy influences patient outcomes.Strong recommendation, low quality of evidence. 6 : ESGE recommends that patients with hemodynamic instability and suspected ongoing bleeding undergo computed tomography angiography before endoscopic or radiologic treatment to locate the site of bleeding.Strong recommendation, low quality evidence. 7 : ESGE recommends withholding vitamin K antagonists in patients with major lower gastrointestinal bleeding and correcting their coagulopathy according to the severity of bleeding and their thrombotic risk. In patients with hemodynamic instability, we recommend administering intravenous vitamin K and four-factor prothrombin complex concentrate (PCC), or fresh frozen plasma if PCC is not available.Strong recommendation, low quality evidence. 8 : ESGE recommends temporarily withholding direct oral anticoagulants at presentation in patients with major lower gastrointestinal bleeding.Strong recommendation, low quality evidence. 9: ESGE does not recommend withholding aspirin in patients taking low dose aspirin for secondary cardiovascular prevention. If withheld, low dose aspirin should be resumed, preferably within 5 days or even earlier if hemostasis is achieved or there is no further evidence of bleeding.Strong recommendation, moderate quality evidence. 10: ESGE does not recommend routinely discontinuing dual antiplatelet therapy (low dose aspirin and a P2Y12 receptor antagonist) before cardiology consultation. Continuation of the aspirin is recommended, whereas the P2Y12 receptor antagonist can be continued or temporarily interrupted according to the severity of bleeding and the ischemic risk. If interrupted, the P2Y12 receptor antagonist should be restarted within 5 days, if still indicated.Strong recommendation, low quality evidence.

Trends in hospitalization, mortality, and timing of colonoscopy in patients with acute lower gastrointestinal bleeding

Background and study aims Current guidelines conditionally recommend performing early colonoscopy (EC) (< 24 hours) in patients admitted with acute lower gastrointestinal bleeding (LGIB). It remains unclear whether this practice is implemented widely. Therefore, we used the Nationwide Inpatient Sample to investigate trends for timing of colonoscopy in patients admitted with acute LGIB. We also assessed trend of hospitalization and mortality in patients with LGIB.

Patients and methods Adult patients with LGIB admitted from 2005 to 2014 were examined. ICD-9-CM codes were used to extract LGIB discharges. Trends were assessed using Cochrane-Armitage test. Factors associated with mortality, cost of hospitalization, and length of stay (LOS) were assessed by multivariable mixed-effects and exact-matched logistic, linear regression, and accelerated-failure time models, respectively.

Results A total of 814,647 patients with LGIB were included. The most common etiology of LGIB was diverticular bleeding (49 %) and 45 % of patients underwent EC. Over the study period, there was no change in the trend of colonoscopy timing. Although admission with LGIB increased over the study period, the mortality rate decreased for patients undergoing colonoscopy. Independent predictors of mortality were age, surgery (colostomy/colectomy) during admission, intensive care unit admission, acute kidney injury, and blood transfusion requirement. Timing of colonoscopy was not associated with mortality benefit. However, cost of hospitalization was $ 1,946 lower and LOS was 1.6 days shorter with EC.

Conclusion Trends in colonoscopy timing in management of LGIB have not changed over the years. EC is associated with lower LOS and cost of hospitalization but it does not appear to improve inpatient mortality.

Sensitive and In Situ Hemoglobin Detection Based on a Graphene Oxide Functionalized Microfiber

The determination of hemoglobin (Hb) level is indispensable in the pathological study of many blood diseases. Graphene oxide (GO), with its excellent optical properties and great biocompatibility, has attracted significant attention and been widely utilized in biochemical detection. Here, we report an ultrasensitive Hb sensor based on a graphene oxide (GO)-coated microfiber. The GO was utilized as a linking layer deposited on the microfiber surface, which can provide an enhanced local evanescent light field and abundant bonding sites for Hb molecules. The optical microfiber with a compact structure and a strong evanescent light field served as the platform for biosensing. The surface morphology characterized by optical microscope, scanning electron microscope, and Raman spectroscopy offers detailed evidence for the success of GO deposition. The dynamic bonding between GO and target Hb molecules was monitored in real-time through an optical spectrum analyzer. An ultrahigh sensitivity of 6.02 nm/(mg/mL) with a detection limit of 0.17 μg/mL was achieved by tracking the resonant wavelength shift of spectra. It is important to highlight that the detection limit of GO-coated microfiber is 1–2 orders of magnitude lower than other reported fiber optic Hb sensors. Benefiting from high sensitivity, low cost, small size, and fast response, the proposed sensing microfiber coated with GO could be a competitive alternative in the diagnosis of blood diseases and a subject of further research in the medical field.