Tes Lab pada Penyakit Infeksi & TropisRuland D.N.Pakasi

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Tes Darah Rutin pada Penyakit Infeksi TropisPengamatan pada:Eri, Leko TrombosManifestasi: anemia, lekositosis atau lekopeni dan DIC*LekositosisUmumnya Netrofil , bentuk muda Netrofilia lanjutinfeksi kronikNetrofilia menghebat + sel mudareaksi leukemoidNon-ganas >25-30 x 10+3/lInflamasi, stress, trauma*Disseminated Intravascular Coagulation

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Tes Darah Rutin pada Penyakit Infeksi TropisLekopeniNetropeni, mis Demam Tifoid, brucellosisInfeksi hebat netropeni hebat prognosis burukPerubahan morfologik pd sepsisDhle bodiesGranula toksik vakuolisasiEosinofilia : non-bakterial, biasanya alergi / infeksi parasit.

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Tes Darah Rutin pada Penyakit Infeksi TropisAnemia bisa timbul sekalipun cadangan besi cukup. Anemia akut: perdarahan/ destruksi eritrosit (misalnya cold agglutinin sehubungan dengan Mycoplasma pneumoniae),Anemia kronik, dengancadangan besi yang normal atau meninggi di sistem retikuloendotelialpenurunan besi dalam plasma serta penurunan TIBC (total iron-binding capacity).

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Tes Darah Rutin pada Penyakit Infeksi TropisInfeksi serius + bakteriemia Gram negatif DIC. (Gram pos jarang)Trombos PT memanjangFDP Fibrinogen Trombosiopenia bisa juga menjadi tanda sepsis bakterial dan bisa bermanfaat dalam mengobservasi respon pasien terhadap terapi.

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Lab Examinations in Dengue Fever (DF)Laboratory findings HematologyLeukopeniaThrombocytopeniaserum aminotransferase (AST, ALT) elevations. The diagnosis is made by Lab Tests seroimmunologyHemagglutination TestsComplement Fixation TestNeutralization TestIgM ELISA or paired serology during recovery or by antigen-detection ELISA or RT-PCR during the acute phase. Virus is readily isolated from blood in the acute phase if mosquito inoculation or mosquito cell culture

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Lab Examinations in Dengue Fever (DF)Hemagglutination TestsVirus + Eri angsaagglutinasi Tes NegatifVirus + serum (ada atb spesifik)tidak aglutinasiTes PositifVirus + Eri + serum (tanpa atb spesifik) aglutiasi Tes negatif

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Lab Examinations in Dengue Fever (DF)Interpretasi

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Lab Examinations in Dengue FeverComplement Fixation TestAg+[serum,Ab pos]+ Complcomplement fixed+RBC(sheep)un lysed : Pos testAg+[serum,Ab neg]+ Complcomplement un fixed RBC(shee) lysed : Neg test

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Dengue Hemorrhagic Fever (General)Tes Lab:ELISA (capture method)Anti-dengue IgMInfeksi primer, akut 7-10 hrIgG (post/kronik)Infeksi sekunder, sesudahnya

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DHF pada AnakIn denguepresent by the 2nd day of feverby the 4th or 5th day, the WBC count 2000 to 4000/mL, 20 to 40% granulocytes. Moderate albuminuria and a few casts may be found. Dengue may be confused with Colorado tick fever, typhus, yellow fever, or other hemorrhagic fevers. Serologic diagnosis may be made by hemagglutination inhibiting and complement fixation tests using paired sera but is complicated by cross-reactions with other flavivirus antibodies.

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DHF pada AnakIn dengue hemorrhagic feverHct > 50%: ipresent during shockWBC count in 1/3 of patients. Coagulaive abnormalitiesThrombocytopenia (< l00,000/mL)positive tourniquet testprolonged PT. Minimal proteinuria may be present. AST levels may be moderately . Serologic tests usually show high complement fixation antibody titers against flaviviruses, suggestive of a secondary immune response.

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DHF pada AnakWHO clinical criteria for diagnosis of dengue hemorrhagic fever:acute onset of high, continuous fever lasts for 2 to 7 dayshemorrhagic manifestations, including at least a positive tourniquet test and petechiae, purpura, ecchymoses, bleeding gums, hematemesis, or melenaHepatomegalythrombocytopenia (< 100,000/mL); or hemoconcentration (Hct increased by > 20%)Those with dengue shock syndrome also have a rapid weak pulse with narrowing of the pulse pressure (< 20 mm Hg) or hypotension with cold, clammy skin and restlessness.

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Herpes SimplexLaboratory tests are generally not necessary (viral cultures and Tzanck smear will confirm diagnosis in patients with atypical presentation)Antibody to appropriate serotypeSeroconversionIncreaseDirect immunofluoroscent antibody slide tests (rapid diagnosis)Tzanck preparationBase of lesionsMultinucleate giant cells

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Herper ZosterLaboratory tests are generally not necessary (viral cultures and Tzanck smear will confirm diagnosis in patients with atypical presentation).The Tzanck preparation shows multinucleate giant cells for both varicella-zoster virus and HSV

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MumpsDarahLekopeniSerum amilase dlm 10 hariSerologiCold agglutinin IgM , max 2 minggu, menetap 6-9 bln; kadar serum konvalesens 4x dpd serum akutTes fiksasi komplemen thd atb positif minggu pertamaBiakanVirus dari ludah 1-5 hariKomplikasiInflamasi testis/ ovarium: lekositosis, LED Pankreatitis: lekositosis, amylase, hiperglikemiaMeningitis: sel LCS < 500/L, mononuclear; glukose normal, protein agak (20-125 mg/dL)

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Morbilli (Measles, Rubeolla)Temuan laboratoriumDarahLekosit , terutama limfo & segmenlekositosissuperinfeksi bakterialSerologi: EIAIgM: fase akut ( 1-2 hari)IgG : >10 hariSekretApusan + pulasan imunofluorosenPulasan Tzank: Multinucleated Giant CellsBiakanBahan: sekret resp & urinIdentifikasi: jaringan

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VaricellaTes lab yang bisa dilakukanSediaan apusBahan: kerokan dasar vesikelPulasan: TzankMultinucleated Giant CellsSensitivitas 60%DarahSerologi:Titer atb serum konvalesen 4x dpd serum akutHemaglutinasiElisaFamaPCR: deteksi DNA virus

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HIV/ AIDSHIV antibody detected by a two-step technique:ELISA as a sensitive screening testConfirmation of positive ELISA tests with the more specific Western blot technique

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Molluscum ContagiousaGiemsa-stainedshows inclusion bodies within many large cells or extracellularly

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Verruca VulgarisDNA typing: circular-doubel-stranded, 8000 bpCross-hybridization> 50% : type seperation< 50%: subtype seperation

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Impetigo/ PyodermaGenerally not necessaryGram stain and C&S to confirm the diagnosis when the clinical presentation is unclearSedimentation rate parallel to activity of the diseaseAnti-DNAse B and antihyaluronidase Urinalysis: hematuria with erythrocyte casts and proteinuria in patients with acute nephritis

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DifteriDiagnosis definitif tergantung pada isolasi C.diphtheriae yang diambil dari bahan di lesi-lesi lokal.Pihak laboratorium harus diberitahukan bahwa bahan disangka difteri agar pihak laboratorium Gram stains of secretions club-shaped organisms, appear as "Chinese letters"

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PolioCSF:Aseptic meningitisElevated WBCsElevated proteinNormal glucose

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Salmonellosis/ Typhoid FeverKulturDarah: positif dlm 10 hari pertamaTinja & Urin: positif dlm minggu 3-5Sumsum tulang:SerologiTes Widal: serum sembuh 4x dpd sakitDarah rutin: Lekopeni

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KoleraIsolasi vibrio cholerae dari bahan tinjaidentifikasi serogroup 01 atau 139Serologi: tes agglutinasi menggunakan antiserum spesifik

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Salmonellosis/ Typhoid FeverOther than a positive culture, no specific laboratory test is diagnostic for enteric fever. In 15 to 25% of cases, leukopenia and neutropenia are detectable. In the majority of cases, the white blood cell count is normal despite high fever. However, leukocytosis can develop in typhoid fever (especially in children) during the first 10 days of the illness, or later if the disease course is complicated by intestinal perforation or secondary infection.

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Salmonellosis/ Typhoid FeverOther nonspecific laboratory resultsTests (AP,GOT,GPT & LDH)The diagnostic "gold standard" is a culture positive for S. typhi or S. paratyphi. 90% during the first week of infection and decrease to 50% by the third week. A low yield is related to low numbers of Salmonella (

Salmonellosis/ Typhoid FeverPositive cultures of stool, urine, rose spots, bone marrow, and gastric or intestinal secretions. Unlike blood cultures, bone marrow cultures remain highly (90%) sensitive.Culture of intestinal secretions (best obtained by a noninvasive duodenal string test) can be positive despite a negative bone marrow culture. If blood, bone marrow, and intestinal secretions are all cultured, the yield of a positive culture is >90%. Stool cultures, while negative in 60 to 70% of cases during the first week, can become positive during the third week of infection in untreated patients. Although the majority of patients (90%) clear bacteria from the stool by the eighth week, a small percentage become chronic carriers and continue to have positive stool cultures for at least 1 year.

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Salmonellosis/ Typhoid FeverSerologic testsWidal test for "febrile agglutinins,high rates of false-positivity and false-negativitynot clinically useful. Polymerase chain reaction and DNA probe assays are being developed

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Disentri basiler/ ShigellosisJumlah Lekosit: , Normal atauSerologi: bisa, jarang bermanfaatTinja:Kultur, harus tinja segar!Mikroskop: LekositPolymerase chain reaction (PCR) may be diagnostic.

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HelmintiasisParasitology study !

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MycosisParasitology study !

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A.Interpretasi Hasil Tes Darah Rutin pada Penyakit Infeksi TropisManifestasi hematologik dapat dilihat pada ke tiga jenis sel darah, yakni eritrosit, lekosit dan trombosit yang tampil berupa anemia, lekositosis, trombositopenia dan Disseminated Intravascular Coagulation (DIC).Pada umumnya penyakit-penyakit infeksi mencetuskan lekositosis dengan peningkatan sel-sel netrofil dan bentuk-bentuk yang lebih muda di dalam peredaran darah tepi. Pada awal tahapan proses infeksi, pertambahan jumlah lekosit dalam sirkulasi berasal dari proses demarginasi; namun begitu, pertambahannya (demikian pula pelepasan bentuk-bentuk mudanya) pada dasarnya disebabkan oleh pengaruh langsung dari interleukin-1 dan interleukin-6 terhadap gudang netrofil di sumsum tulang. Netrofilia yang tetap-tinggi, yang dijumpai pada penyakit infeksi kronik, tampaknya disebabkan diwadahi oleh colony-stimulating factors yang dilepaskan oleh sel-sel makrofag, limfosit dan jaringan lainnya. Menghebatnya fenomena ini bisa menimbulkan reaksi-reaksi leukemoid, yakni dengan pelepasan lekosit-lekosit muda ke dalam sirkulasi dalam jumlah banyak. Reaksi eukemoid ditandai dengan jumlah lekosit non-ganas > 25-30 x 109/L; umumnya sel-sel ini mencerminkan respon dari sumsum tulang yang sehat terhadap sitokin sebagai akibat dari trauma, inflamasi dan ketegangan-ketegangan (stress) lainnya. Sebaliknya, pada beberapa infeksi (misalnya demam tifois, bruselosis) biasanya terjadi netropeni. Pada infeksi yang hebat, sumsum tulang tidak mampu menjaga/ mempertahan kan netrofil-netrofil di perifer dan menjurus kepada netropenia hebat; hal ini sering menjadi petanda prognosis buruk. Perubahan-perubahan morfologik (misalnya Dhle bodies, granulasi toksik, vakuolisasi) bisa ditemukan pada netrofil-netrofil dari asien-pasien dengan sepsis. Eosinofilia mengilhami suatu penyebab yang non-bakterial, biasanya alergi atau infeksi parasit.Anemia bisa timbul sekalipun cadangan besi cukup. Anemia bisa terjadi akut, sebagai akibat dari perdarahan atau perusakan/ destruksi eritrosit (misalnya cold agglutinin sehubungan dengan Mycoplasma pneumoniae), atau berlangsung kronik, dengan cadangan besi yang normal atau meninggi di sistem retikuloendotelial dan penurunan besi dalam plasma serta penurunan TIBC (total iron-binding capacity).Infeksi serius dengan bakteriemia oleh bakteri gram negatif lebih umum menyebabkan DIC (disseminated intravascular coagulation) daripada bakteri gram positif. TNF (tumor necrotizing factor) dapat memainkan peran integral dalam memunculkan DIC dengan jalan menginduksi sel-sel endotelial mencetuskan atkivitas faktor prokoagulan jaringan. DIC ditandai dengan adanya trombositopenia, PT (Prothrombin time) memanjang, peninggian kadar FDP (fibrin degradation product) dan penurunan kadar fibrinogen. Komplikasi-komplikasi yang bisa terjadi mencakupi perdarahan dan/ atau trombosis dengan perdarahan yang paradoksal walaupun dengan status hiperkoagulabelnya. Penanganan terhadap penyakit yang mendasarinya sangat penting untuk memulihkan DIC.Trombosiopenia bisa juga menjadi tanda sepsis bakterial dan bisa bermanfaat dalam mengobservasi respon pasien terhadap terapi.After an incubation period of 2 to 7 days, the typical patient experiences the sudden onset of fever, headache, retroorbital pain, and back pain along with the severe myalgia that gave rise to the colloquial designation "break-bone fever." There is often a macular rash on the first day as well as adenopathy, palatal vesicles, and scleral injection. The illness may last a week, with additional symptoms usually including anorexia, nausea or vomiting, marked cutaneous hypersensitivity, andnear the time of defervescencea maculopapular rash beginning on the trunk and spreading to the extremities and the face. Epistaxis and scattered petechiae are often noted in uncomplicated dengue, and preexisting gastrointestinal lesions may bleed during the acute illness.Laboratory findings include leukopenia, thrombocytopenia, and, in many cases, serum aminotransferase* elevations. The diagnosis is made by IgM ELISA or paired serology during recovery or by antigen-detection ELISA or RT-PCR during the acute phase. Virus is readily isolated from blood in the acute phase if mosquito inoculation or mosquito cell culture is used.*Aminotransferase: AST (Apartate aminotransferase = SGOT,Serum Glutamate Oxaloacetate Transaminase) + ALT (Alanine aminotransferase = SGPT, Serum Glutamate Pyruvate Transaminase )

Tes HemagglutinasiVirus Dengue bisa mengagglutinasi Eri Angsa tetapi agglutinasi tidak terjadi bila dalam serum ada antibodi homolog, jadi:Virus + Eri angsaagglutinasi Tes NegatifVirus + serum (ada atb spesifik)tidak aglutinasiTes PositifVirus + Eri + serum (tanpa atb spesifik) aglutiasi Tes negatifUji Fiksasi KomplemenAg + serum P (ada Ab)+ komplemenkomplemen akan diikat oleh komplek Ag:Abtak ada komplemen bebas tersisa.Jika kemudian di+ eri domba yang sensitized (oleh anti-eri domba) tak terjadi hemolisis disebut tes positif.Bila serum tak ada Ab tak ada Ag:Ab komplemen bebas; bila di+ eri domba lisis tes negatif.Prosedur Laboratorium:1.ELISA (Enzyme-linked immunolinked assay:In dengue, leukopenia is present by the 2nd day of fever; by the 4th or 5th day, the WBC count has dropped to 2000 to 4000/mL with only 20 to 40% granulocytes. Moderate albuminuria and a few casts may be found. Dengue may be confused with Colorado tick fever, typhus, yellow fever, or other hemorrhagic fevers. Serologic diagnosis may be made by hemagglutination inhibiting and complement fixation tests using paired sera but is complicated by cross-reactions with other flavivirus antibodies.In dengue hemorrhagic fever, hemoconcentration (Hct > 50%) is present during shock; the WBC count is elevated in 1/3 of patients. Thrombocytopenia (< l00,000/mL), a positive tourniquet test, and a prolonged prothrombin time are characteristic and indicative of the coagulation abnormalities. Minimal proteinuria may be present. AST levels may be moderately increased. Serologic tests usually show high complement fixation antibody titers against flaviviruses, suggestive of a secondary immune response.The WHO has established clinical criteria for diagnosis of dengue hemorrhagic fever, which is a medical emergency: acute onset of high, continuous fever that lasts for 2 to 7 days; hemorrhagic manifestations, including at least a positive tourniquet test and petechiae, purpura, ecchymoses, bleeding gums, hematemesis, or melena; hepatomegaly; thrombocytopenia (< 100,000/mL); or hemoconcentration (Hct increased by > 20%). Those with dengue shock syndrome also have a rapid weak pulse with narrowing of the pulse pressure (< 20 mm Hg) or hypotension with cold, clammy skin and restlessness.

In dengue hemorrhagic fever hemoconcentration (Hct > 50%) is present during shock; the WBC count is elevated in 1/3 of patients. Thrombocytopenia (< l00,000/mL), a positive tourniquet test, and a prolonged prothrombin time are characteristic and indicative of the coagulation abnormalities. Minimal proteinuria may be present. AST levels may be moderately increased. Serologic tests usually show high complement fixation antibody titers against flaviviruses, suggestive of a secondary immune response.

The WHO has established clinical criteria for diagnosis of dengue hemorrhagic fever, which is a medical emergency: acute onset of high, continuous fever that lasts for 2 to 7 days; hemorrhagic manifestations, including at least a positive tourniquet test and petechiae, purpura, ecchymoses, bleeding gums, hematemesis, or melena; hepatomegaly; thrombocytopenia (< 100,000/mL); or hemoconcentration (Hct increased by > 20%). Those with dengue shock syndrome also have a rapid weak pulse with narrowing of the pulse pressure (< 20 mm Hg) or hypotension with cold, clammy skin and restlessness.

Ferri: Laboratory tests are generally not necessary (viral cultures and Tzanck smear will confirm diagnosis in patients with atypical presentation).Merck: Diagnosis is confirmed by cultures for the virus, seroconversion and a progressive increase in serum antibodies to the appropriate serotype (in primary infections), and biopsy findings. A Tzanck preparation of the base of a lesion often reveals multinucleate giant cells in HSV or varicella-zoster virus infection. Newer techniques such as the polymerase chain reaction of CSF may allow early noninvasive diagnosis of herpes simplex encephalitis.HSV should be distinguished from herpes zoster, which rarely recurs and usually causes more severe pain and larger groups of lesions distributed along a dermatome. Differential diagnosis includes varicella, genital ulcers or gingivostomatitis due to other causes, and vesicular dermatoses, particularly dermatitis herpetiformis and drug eruptions.Ferri: Laboratory tests are generally not necessary (viral cultures and Tzanck smear will confirm diagnosis in patients with atypical presentation).Merck: The Tzanck preparation shows multinucleate giant cells for both varicella-zoster virus and HSV

MumpsSerum & Urine amylase dalam 10 hari pertama (asal kel ludah)LekopeniaCold agglutinins IgM max dalam 2 minggu pertama, tetap ada 6-9 bulan; menunjukkan infeksi baruComplement fixation test thd antibodi positif dalam 1 minggu pertama, tetap tinggi sampai > 6 minggu; convalescent sera 4x dpdt acute pahse seraIsolasi virus dal ludah sp 5 hari setelah serangan/gejala kel ludah.Komplikasi:Inflamasi testis/ ovarium: lekositosis, LED Pankreatitis: lekositosis, amylase, hiperglikemiaMeningitis: sel LCS < 500/L, mononuclear; glukose normal, protein agak (20-125 mg/dL)Isolasi virus pada hari pertama gejala Morbilli (Measles, Rubeolla)Temuan-temuan laboratorium Lekopeni, terutama limfopeni dan netropeni; hal ini disebabkan oleh invasi virus ke lekosit-lekosit dan berlanjut dengan kematian sel. Bila terjadi lekositosis, ini memberi kesan adanya superinfeksi bakterial.Tes cairan otak dilakukan jika ada ensefalitis oleh varicella, pada cairan ini bisa dijumpai peninggian kadar protein dan lekositosis.Diagnosis spesifik bisa dilakukan dengan cepat menggunakan pulasan imuno fluorosen pada sediaan apus sekret dari saluran pernapasan. Untuk teknik ini dibutuhkan antibodi monoklonal yang digandengkan dengan fluorosen. Sekret ini juga bisa digunakan untu menemukan multinucleated giant cell Isolasi virus dapat diambil dari sekret saluran napas dan urin kemudian diidentifika si pada biakan jaringanSerodiagnosis yang lebih cepat dan sederhana adalah cara EIA (Enzymeimmuno assay) untuk antibodi IgM dan IgG. IgM bisa dideteksi dalam 1-2 hari setelah munculnya ruam (rash) sedang IgG meningkat nyata setelah 10 hari.VaricellaLABORATORY FINDINGSKonfirmasi diagnosis varicella hanya dimungkinkan melalui 3 cara, yaitu isolasi virus varicella, terjadinya serokonversi atau meningkatnya titer antibodi dari serum fase akut sebesar 4x pada serum konvalesen, atau mendeteksi DNA virus varicella melalui teknik Polymerase Chain Reaction (PCR).Cara cepat untuk memperoleh kesan varicella bisa dilakukan dengan sediaan apus menggunakan pulasan Tzank. Bahan apusan diambil melalui kerokan pada dasar vesikel lesi dan dicari adanya sel raksasa dengan iti ganda (multinucleated giant cell). Sayang, sensitivitas metode ini rendah (60%).Tes serologik yang paling sering digunakan untuk menilai respon tubuh adalah:secara imunofluorosensi mendeteksi adanya antibodi terhadap antigen membran virus (FAMA, fluoroscent antigen membrane assay), hemagglutinasi, dan Enzyme-linked im munosorbent assay (ELISA). Tes FAMA dan ELISA adalah yang peling sensitif. Ferri: Generally not indicated in children Merck: Giemsa-stained, shows inclusion bodies within many large cells or extracellularly

Merck: Wart viruses contain circular, double-stranded DNA, with about 8000 base pairs. Each type is indicated by a number and generally causes clinically distinct lesions (see Table 1151). To qualify as a separate type, DNA cross-hybridization must be < 50%; for subtypes, > 50%. Although DNA is distinctive, most HPVs, including those of bovine origin, share a protein antigen that can be shown histologically on fixed tissue with a test that is positive for all types of HPV and is useful for diagnosis. When HPVs become oncogenic, however, they no longer stain positive and cannot be seen with the electron microscope. Oncogenic HPV DNA can thus be found in malignant warts by modern molecular hybridization DNA techniques. DNA typing is now available in only a few research laboratories but is important for prognosis of genital warts and their consequences.

Ferri: Generally not necessaryGram stain and C&S to confirm the diagnosis when the clinical presentation is unclearSedimentation rate parallel to activity of the diseaseIncreased anti-DNAse B and antihyaluronidaseUrinalysis revealing hematuria with erythrocyte casts and proteinuria in patients with acute nephritis (most frequently occurring in children between 2 and 4 yr of age in the southern part of the U.S.)

DifteriDiagnosis definitif tergantung pada isolasi C.diphtheriae yang diambil dari bahan di lesi-lesi lokal.Pihak laboratorium harus diberitahukan bahwa bahan disangka difteri agar pihak laboratorium.Sediaan apus dari sekret diwarni dengan pulasan Gram akan memperlihatkan organisme-organisme berbentuk club dan kelihatan seperti tulisan/huruf cinaFerri:CSF:Aseptic meningitisElevated WBCsElevated proteinNormal glucose

Merck: The diagnosis is confirmed by isolation of V. cholerae in cultures from direct rectal swabs or fresh stools and its subsequent identification as serogroup 01 or 0139 through agglutination by specific antiserum.

Ferri:Total WBCs may be low, normal, or high.Stool should be cultured from fresh samples, because the yield is increased by processing the specimen soon after passage.Serology is available but rarely useful.Polymerase chain reaction may be diagnostic.Fecal leukocyte preparation may show WBCs. HarrisonOther than a positive culture, no specific laboratory test is diagnostic for enteric fever. In 15 to 25% of cases, leukopenia and neutropenia are detectable. In the majority of cases, the white blood cell count is normal despite high fever. However, leukocytosis can develop in typhoid fever (especially in children) during the first 10 days of the illness, or later if the disease course is complicated by intestinal perforation or secondary infection. Other nonspecific laboratory results include moderately elevated values in liver function tests (aminotransferases, alkaline phosphatase, and lactate dehydrogenase). In addition, nonspecific ST and T wave abnormalities can be seen on electrocardiograms.The diagnostic "gold standard" is a culture positive for S. typhi or S. paratyphi. The yield of blood cultures is quite variable: it can be as high as 90% during the first week of infection and decrease to 50% by the third week. A low yield is related to low numbers of Salmonella (90%. Stool cultures, while negative in 60 to 70% of cases during the first week, can become positive during the third week of infection in untreated patients. Although the majority of patients (90%) clear bacteria from the stool by the eighth week, a small percentage become chronic carriers and continue to have positive stool cultures for at least 1 year.Several serologic tests, including the classic Widal test for "febrile agglutinins," are available; however, given high rates of false-positivity and false-negativity, these tests are not clinically useful. Polymerase chain reaction and DNA probe assays are being developed

Other nonspecific laboratory results include moderately elevated values in liver function tests (aminotransferases, alkaline phosphatase, and lactate dehydrogenase). In addition, nonspecific ST and T wave abnormalities can be seen on electrocardiogramsThe diagnostic "gold standard" is a culture positive for S. typhi or S. paratyphi. The yield of blood cultures is quite variable: it can be as high as 90% during the first week of infection and decrease to 50% by the third week. A low yield is related to low numbers of Salmonella (90%. Stool cultures, while negative in 60 to 70% of cases during the first week, can become positive during the third week of infection in untreated patients. Although the majority of patients (90%) clear bacteria from the stool by the eighth week, a small percentage become chronic carriers and continue to have positive stool cultures for at least 1 year.

Several serologic tests, including the classic Widal test for "febrile agglutinins," are available; however, given high rates of false-positivity and false-negativity, these tests are not clinically useful. Polymerase chain reaction and DNA probe assays are being developed