慢性乙型肝炎肝纖維化無創(chuàng)診斷的進展

徐　瑞　常　江　黃　華　計洋洋　鄧振華

昆明醫(yī)科大學第二附屬醫(yī)院消化內科一病區(qū)(650101)

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慢性乙型肝炎肝纖維化無創(chuàng)診斷的進展

徐瑞常江*黃華計洋洋鄧振華

昆明醫(yī)科大學第二附屬醫(yī)院消化內科一病區(qū)(650101)

摘要慢性乙型肝炎(CHB)為肝纖維化的常見原因之一，肝纖維化的正確評估對治療決策和預后判斷十分重要。肝活檢是診斷肝纖維化的金標準，但其為侵入性檢查，費用高，重復性差，患者不易接受，故迫切需要探索肝纖維化的無創(chuàng)診斷方法。近年發(fā)現(xiàn)彈性成像技術、血清學指標以及多個血清學指標構成的診斷模型對肝纖維化具有診斷價值。本文就CHB肝纖維化的無創(chuàng)診斷進展作一綜述。

關鍵詞乙型肝炎，慢性；肝硬化；診斷

肝纖維化是肝硬化和肝衰竭的早期信號，亦是抗病毒治療的指征。肝活檢是診斷肝纖維化的金標準，但其為有創(chuàng)性檢查，有發(fā)生膽汁性腹膜炎、氣胸、腹腔內出血等并發(fā)癥的風險，且肝活檢不便于動態(tài)監(jiān)測肝纖維化的進展過程。因此，需要探索診斷肝纖維化的無創(chuàng)方法。本文就慢性乙型肝炎(chronic hepatitis B, CHB)肝纖維化的無創(chuàng)診斷進展作一綜述。

一、超聲彈性成像技術

1. 瞬時彈性成像(transient elastography, TE)：TE是一項通過測量肝臟硬度間接反映肝纖維化的超聲技術[1]。檢測的肝實質相當于整個肝臟的1/500，為肝活檢樣本的100倍，更具有代表性[2]。目前歐洲肝病研究協(xié)會(EASL)臨床指南[3]推薦將TE作為診斷CHB肝纖維化的方法。國內Jia等[4]發(fā)現(xiàn)，當肝臟硬度測定值(LSM)為7.3 kPa時，TE診斷CHB明顯肝纖維化的受試者工作特征曲線下面積(AUROC)為0.82；臨界值為10.7 kPa時，診斷肝硬化的AUROC達0.90。TE還可用于監(jiān)測CHB患者抗病毒治療后肝纖維化的改善情況[5]，評估食管胃底靜脈曲張、肝癌等并發(fā)癥發(fā)生的風險以及預后[2]。近期研究發(fā)現(xiàn)，M型探頭TE可測量受控的衰減參數(shù)，對CHB患者肝脂肪變的評估具有較高的敏感性和特異性[6]，而CHB患者發(fā)生肝脂肪變可影響抗病毒的療效，增加肝硬化和肝癌的發(fā)生風險[6-7]。

體重指數(shù)(BMI)可影響TE對肝纖維化的診斷。對BMI≥30 kg/m2的患者，M型探頭診斷肝纖維化的失敗率達29.1%。XL型探頭(2.5 MHz)的頻率較M型探頭更低，振幅更大，穿透力更強，其診斷BMI≥30 kg/m2者的肝纖維化失敗率僅6.8%[8]。此外，肝血管瘤、肝衰竭、肝右葉占位、腹水、血清總膽紅素、肝臟炎癥程度亦可影響TE對肝纖維化的診斷[4,8-9]。進食亦可能影響TE對肝纖維化診斷的準確性[10]，建議行TE前至少空腹2 h[8]。

2. 實時組織彈性成像(real-time elastography, RTE)：與TE相比，RTE是二維圖像，不受腹水、肋間隙狹窄、肝脂肪變、肝萎縮等因素的影響[8]。Xie等[11]發(fā)現(xiàn)，肝臟彈性指數(shù)的臨界值為1.10時，RTE診斷CHB患者≥S2期肝纖維化的敏感性為77.8%，特異性80.0%，陽性預測值(PPV)80%，AUROC為0.863；臨界值為0.60時，診斷肝硬化的敏感性50.0%，特異性96.7%，陰性預測值(NPV)92.2%，AUROC為0.797。

3. 聲脈沖輻射力成像(acoustic radiation force impulse, ARFI)：ARFI通過向肝組織發(fā)出高強度的聲脈沖，對組織進行短時間的機械刺激，從而產(chǎn)生剪切波。剪切波的速度(shear-wave velocity, SWV)與肝臟硬度有關[12]。Friedrich-Rust等[13]首次應用ARFI評估CHB患者肝纖維化程度，SWV臨界值為1.39 m/s時，診斷明顯肝纖維化的特異性為90%，PPV 67%，AUROC 0.75。ARFI在B超引導下選擇感興趣的區(qū)域進行測量，可避免周圍組織(如血管)的干擾[14]。對合并腹水或肝右葉占位的CHB患者亦適用[8]。但SWV的范圍值較窄(0.5～4.4 m/s)，對肝纖維化分期臨界值的界定帶來了一定困難[8]。肥胖、ALT、進食、膽汁淤積可影響ARFI對肝纖維化分期的診斷[15-17]。

4. 剪切波彈性成像：二維剪切波彈性成像(2D-SWE)可測量SWV，與普通超聲設備聯(lián)合使用具有較好的重復性，可用于長期隨訪，此外，2D-SWE能建立一個實時、二維的量化圖[12,18]。當LSM臨界值分別為7.2 kPa、9.1 kPa、11.7 kPa時，診斷CHB明顯肝纖維化(F≥2)、重度肝纖維化(F≥3)、肝硬化(F=4)的準確性高，NPV分別為82.6%、95.1%、97.4%，AUROC均達0.900以上，但BMI、GGT、血清白蛋白可影響2D-SWE對肝纖維化分期診斷的準確性[18]。點剪切波彈性成像(PSWE)對CHB肝纖維化分期亦有診斷價值，且重復性好[19]。

二、影像學技術

1. 磁共振彈性成像(magnetic resonance elastography, MRE)：MRE可測量整個肝臟，對F≥1、F≥2、F≥3、F=4期肝纖維化診斷的準確性較高，AUROC達0.960以上。且不受肥胖、腹水的影響，同時可定量診斷肝臟脂肪化、鐵沉積的程度。但當LSM的臨界值為3.61 kPa時，MRE診斷F≥1的肝纖維化的NPV較低(0.677)，提示MRE將肝纖維化F≥1的患者誤診為F=0的概率較大。對F≤2期的CHB患者，炎癥可使MRE高估或低估肝臟纖維化的程度[20]。

2. 磁共振擴散加權成像(diffusion weighted imaging, DWI)：DWI可顯示肝纖維化時水在肝臟擴散的情況，然而，由于掃描設備、序列和b值的選擇等因素的不同，DWI的表觀擴散系數(shù)(ADC)在各期肝纖維化間存在較多重疊，目前未發(fā)現(xiàn)診斷肝纖維化的最佳臨界值[21]。

3. 其他磁共振技術：增強磁共振顯示肝纖維化時肝臟血流動力學改變，核磁波譜分析(MRS)從功能方面評價肝纖維化時肝臟代謝的變化，對肝纖維化的臨床有一定價值，但MRI對肝纖維化的診斷易受呼吸、胃腸道運動的影響。目前掃描序列、成像參數(shù)的選擇和數(shù)據(jù)的獲得均缺乏統(tǒng)一標準[22]。因此，磁共振技術對CHB肝纖維化的診斷價值仍有待研究。

4. CT灌注成像：可應用定量參數(shù)反映肝纖維化血流灌注情況，肝臟血流灌注變化與病變嚴重程度有關，但參數(shù)受呼吸運動的影響較大，不同灌注模型設計和計算方法對結果亦有一定影響，目前的研究尚缺乏嚴格的灌注參數(shù)與病理對照[23]。

三、血清學指標

1. 平均血小板體積(MPV)：肝纖維化時，血小板生存周期縮短以及白細胞介素(IL)-6增加均可刺激骨髓產(chǎn)生血小板，使釋放至外周血的新生血小板增加，從而導致MPV明顯升高[24]。MPV臨界值為8.15 fl時，診斷重度肝纖維化的AUROC為0.677，敏感性67%，特異性63%[25]。

2. 紅細胞分布寬度(RDW)：CHB患者由于炎癥、營養(yǎng)物質缺乏、骨髓抑制、氧化應激，可致RDW升高[26]。Karagoz等[25]發(fā)現(xiàn)RDW≥12.6%診斷重度肝纖維化的AUROC為0.672，敏感性91.5%，特異性42.5%。

3. 其他血清學指標：血清轉鐵蛋白[27]、血清銅藍蛋白[28]可反映CHB肝纖維化的嚴重程度，有望成為評估CHB肝纖維化的血清學指標。

4. RDW與血小板計數(shù)比值(RPR)：Chen等[29]的研究結果顯示RPR與肝纖維化相關(P<0.001)，RPR的臨界值分別為0.10、0.16時，診斷CHB明顯肝纖維化、肝硬化的AUROC分別為0.825、0.884，敏感性分別為63.1%、73.7%，特異性分別為85.5%、93%，PPV分別為77.4%、60.8%，NPV分別為74.7%、96%。

5. 球蛋白/血小板計數(shù)(GP)模型：GP模型與肝纖維化嚴重程度相關(P<0.001)，GP值<1.68，診斷輕微肝纖維化的AUROC為0.762，敏感性72.4%，特異性69.6%；GP值>2.53，診斷肝硬化的AUROC為0.781，敏感性72.7%，特異性84.5%[30]。

6. 白蛋白、Ⅳ型膠原、脾臟縱向直徑構成的評分系統(tǒng)：該系統(tǒng)評分<3分，排除明顯肝纖維化的NPV 86.1%，敏感性86.8%；評分>6時，診斷明顯肝纖維化的AUROC為0.79，PPV 73.6%，特異性87.6%；該系統(tǒng)可使53.4%的患者避免行肝穿刺[31]。

7. REAL TEST公式：REAL TEST公式值≥1.37時，診斷CHB明顯肝纖維化的AUROC為0.852，敏感性78%，特異性79%，NPV 85%，PPV 70%；該公式值≥0.64時，診斷輕微肝纖維化的AUROC為0.724 2，PPV 94.58%，敏感性71.75%，特異性56.94%[32]。

8. FibroTest模型：該模型的臨界值分別為0.32、0.68時，診斷CHB明顯肝纖維化、肝硬化的敏感性分別為79.3%、80.0%，特異性分別為93.3%、84%，PPV分別為98.5%、75.9%，AUROC分別為90.3%，86.6%[33]。但由于該模型包含觸珠蛋白、膽紅素、γ-GGT，患者發(fā)生溶血、膽汁淤積或近期有飲酒史時，可出現(xiàn)假陽性結果[34]。

9. APRI模型：Zhu等[35]發(fā)現(xiàn)，APRI的臨界值分別為0.5、1.0時，診斷ALT≤2倍正常值上限(ULN)的CHB患者發(fā)生明顯肝纖維化、肝硬化的AUROC分別為0.81、0.83，敏感性分別為82%、75.9%，特異性分別為83.3%、69.2%，NPV分別為89.9%、93.5%。

10. FIB-4模型：Zhu等[35]還發(fā)現(xiàn)，F(xiàn)IB-4的臨界值為1.7時，診斷ALT≤2×ULN CHB明顯肝纖維化的敏感性74%，特異性84.4%，PPV 71.2%，AUROC為0.86；臨界值為1.9時，診斷肝硬化的AUROC為0.77，敏感性為69%，特異性75.3%，NPV 92.4%。

11. Forns指數(shù)：Forns指數(shù)對CHB肝纖維化的預測價值鮮見報道，饒建國等[36]對361例接受肝穿刺檢查的CHB患者行Forns指數(shù)預測。臨界值分別為4.873、5.432、6.289，診斷CHB顯著肝纖維化、嚴重肝纖維化、肝硬化的AUROC均>0.7，提示Forns指數(shù)可作為評估CHB肝纖維化的無創(chuàng)方法。

四、血清學指標聯(lián)合彈性成像技術

由于血清學指標與彈性成像技術可從不同的側面對肝纖維化進行診斷，因此，兩者聯(lián)合可起到互補的作用，提高診斷肝纖維化的準確性。ARFI、TE、APRI聯(lián)合診斷明顯肝纖維化、肝硬化的準確性可分別升至83.86%、91.88%，敏感性和NPV亦明顯提高[14]。Forns指數(shù)與ARFI或TE聯(lián)合以及FibroSURE與AST聯(lián)合亦可提高診斷CHB肝纖維化分期的準確性[37-38]。

五、結語

TE對CHB肝纖維化分期具有診斷價值，但對肝纖維化早期的診斷價值較低。目前ARFI、RTE、MRE、剪切波彈性成像對CHB肝纖維化也具有診斷價值，但缺乏充分的臨床數(shù)據(jù)支持[39]。血清學指標具有重復性高、容易獲得等優(yōu)點，但需多中心大樣本的臨床研究來進一步評估其診斷價值。血清學指標聯(lián)合彈性成像技術可提高診斷的準確性，但如何聯(lián)合為一大難題[14]。

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(2015-08-11收稿；2015-09-18修回)

DOI:10.3969/j.issn.1008-7125.2016.06.013

Progress in Noninvasive Assessment of Liver Fibrosis in Patients with Chronic Hepatitis B

XURui,CHANGJiang,HUANGHua,JIYangyang,DENGZhenhua.

DepartmentofGastroenterology,theSecondAffiliatedHospitalofKunmingMedicalUniversity,Kunming(650101)

Correspondence to: CHANG Jiang, Email: cjcjchangjiang@sina.com

AbstractChronic hepatitis B (CHB) is one of the most commom cause of liver fibrosis. Accurate assessment of liver fibrosis is essential for the strategy of treatment and judgement of prognosis . Liver biopsy is the gold standard for staging fibrosis, but it is invasive with high cost, low reproducibility and poor acceptance by patients. Therefore, it is urgent to explore a noninvasive modality for the assessment of liver fibrosis. Recent evidence highlights that elastographic techniques, biochemical markers and the diagnostic model consisted of several serum markers have the potential for the diagnosis of liver fibrosis. This article reviewed the progress in noninvasive assessment of liver fibrosis in patients with CHB.

Key wordsHepatitis B, Chronic;Liver Cirrhosis;Diagnosis

*本文通信作者，Email: cjcjchangjiang@sina.com