LAB. DIAGNOSIS OF DENGUE FEVER

"IT EXPLAINS LABORATORY WORKUP AND CLINICAL CO-RELATION IN DENGUE FEVER AND DENGUE HEMORRHAGIC FEVER."

THE EARLIEST CHANGE DETECTABLE ON LABORATORY INVESTIGATIONS IS A LOW WHITE BLOOD CELL COUNT, WHICH MAY THEN BE FOLLOWED BY LOW PLATELET COUNT.

CBC, SHOWS LEUKOPENIA i.e LOW TLC,WHICH STARTS FIRST AND RECOVERS FIRST ,THEN THROMBOCYTOPENIA i.e LOW PLATELET COUNT, STARTS LATER AND RECOVERS LATER.

IF HCT DECREASES DURING FEBRILE PHASE, IT INDICATES EITHER UNNECESSARY I/V OR ORAL FLUIDS.

IF HCT RISES MORE THAN 20% OF INTIAL VALUE ,IT INDICATES PLASMA LEAK.

INCREASE IN LYMPHOCYTE COUNT IS ALSO SUGGESTIVE OF PLASMA LEAK.

URINE C/E .HELPS TO DIAGNOSE UTI.

NS1-NON STRUCTURAL PROTEIN- 1 IS POSITIVE WITHIN 05 DAYS OF INFECTION AND NS1 >600 IS INDICATIVE OF DHF.

DIABETICS SHOULD HAVE THEIR BLOOD SUGAR DONE TWICE A DAY AND LEVEL SHOULD BE AROUND 180mg/100ml OR LESS THAN 10MMOL/L, AVOID HYPOGLYCAEMIA. .

ON ULTRASOUND GALLBLDDER EDEMA, PERICHOLECYSTIC FLUID COLLECTION, ASCITES OR PLEURAL EFFUSION MAY ASSIST IN THE EARLY IDENTIFICATION OF PLASMA LEAK IN DHF.

IF IN CRITICAL PHASE HCT IS DECREASING AFTER THE INTIAL RISE, IT MAY INDICATE REABSORPTION OF FLUID FROM THE THIRD SPACE.

DECREASING HCT WITH DECREASE IN HB. IS INDICATIVE OF HEMORRHAGE.

ANTI DENGUE IgM, IgG NOT ROUTINELY USED DURING EPIDEMIC PCR FOR DENGUE TYPING NOT ROUTINELY USED

ANTI DENGUE IgM BECOMES POSITIVE 6-10TH DAY AND REMAINS POSITIVE FOR 2-3 MONTHS.

IgG POSITIVE SHOWS PREVIOUS DENGUE INFECTION BUT RISE ABOVE 1280 IS INDICATIVE OF SEC. INFECTION BY HETEROTYPIC STRAIN.

IN THIS HETEROTYPIC INFECTION IgG RESPONSE IS MUCH INCREASED BUT IgM RESPONSE IS BLUNTED AND IgM/IgG WILL BE < 1.2.

IgM ANTI BODIES DO NOT CROSS PLACENTAL BARRIER BUT IgG ANTIBODIES CAN.

SPECIFIC SCREENING TEST FOR DENGUE FEVER.

TEST METHOD	DETECTION	COMMENTS
DENGUE NSI ANTIGEN	DAY 1-5	PRESENCE OF NON STRUCTURAL PROTEIN 1
DENGUE REAL TIME PCR	DAY 1-5	PRESENCE OF DENGUE VIRUS RNA
DENGUE Ig M ANTIBODIES	DAY 5 ONWARD	INDICATES ACUTE RECENT INFECTION
DENGUE Ig G ANTIBODIES	DAY 5 ONWARD	HIGH LEVELS IN SECONDRY DENGUE INFECTION

CLINICAL INTERPRETATION OF ANTI DNGUE 1g M

<0.9 NEGATIVE

0.9-1.1 BORDER LINE

1.1 POSITIVE

IF HCT RISES MORE THAN 20% OF INTIAL VALUE IS INDICATIVE OF PLASMA LEAK .OTHER POINTERS ARE RAPID FALL IN PLATELET COUNT AND INCREASED LYMPHOCYTE % IN CBC.

S/ELECTROLYTES
THERE MAY BE HYPONATREMIA,HYPOGLYCAEMIA, HYPOCALCAEMIA, HYPOPROTEINAEMIA, HYPOKALAEMIA,

S/ALBUMEN < 3.5 OR DECREASE MORE THAN O.5 IN 24 HRS IN ASCITIES, S/CHOLESTEROL < 100 OR DROP OF MORE THAN 20 IN 24HOURS.

X-RAY CHEST RT. LATERAL DECUBITUS VIEW TO DETECT SMALL PLEURAL EFFUSION BUT U/S IS PREFERABLE IF AVAILABLE.

IN DHF PLASMA LEAKAGE RESULTS IN HEMOCONCENTRATION (AS INDICATED BY A RISING HEMATOCRIT MORE THAN 20%) HYPOALBUMINEMIA LESS THAN 3.5 OR DROP >0.5 , .CHOLESTEROL LEVEL < 100 OR DROP > 20 IN 24 HOURS.

IN ALL DHF PATIENTS DO NOT FORGET TO MONITOR RENAL FUNCTION AND LIVER FUNCTION.