Fever after return from a tropical country

• To be done the same day, without waiting for a fever peak. The result must be returned within 2 hours of receipt at the laboratory, and no later than 4 hours after sampling: otherwise, or in the presence of a sign of severity, refer to the emergency department. State on the prescription the country, the date of return and the chemoprophylaxis.

Laboratory tests

• Thin and thick blood film (search for Plasmodium)
• Rapid diagnostic test for malaria (HRP2 antigen)if neededIf the laboratory does not do a thick film or a sensitive technique: the combination of thin film and RDT is the accepted alternative; the RDT must detect the HRP2 antigen ^[2]; it is covered in addition to the film ^[3].
• FBC with platelets
• CRP
• Serum creatinine with eGFR
• AST
• ALT
• Bilirubin
• Plasma glucoseif neededConfirmed P. falciparum malaria: its identification must be accompanied by a search for laboratory signs of severity, including hypoglycaemia (< 2.2 mmol/L) and acidosis (bicarbonate < 15 mmol/L); outpatient treatment is possible only in the absence of any laboratory sign of severity ^[2].
• Bicarbonate (confirmed malaria: laboratory signs of severity)if neededConfirmed P. falciparum malaria: its identification must be accompanied by a search for laboratory signs of severity, including hypoglycaemia (< 2.2 mmol/L) and acidosis (bicarbonate < 15 mmol/L); outpatient treatment is possible only in the absence of any laboratory sign of severity ^[2].
• Blood cultures
• HIV serology
• Urine dipstick, then urine microscopy and culture if positive

12 to 24 hours later if the first result is negative or doubtful

• Repeat thin and thick blood film (or film and RDT)if neededFirst result negative or doubtful (notably with the combination of thin film and RDT, whose sensitivity is not optimal): repeat the diagnostic test 12 to 24 hours later ^[2].

• State on the prescription the date of onset of signs and the area of stay. Malaria must still be ruled out urgently (previous tab).

Laboratory tests

• Dengue and chikungunya RT-PCR (day 1 to day 7 of signs)if neededReturn from an affected area, suggestive symptoms, sample up to day 7 after the onset of signs ^[3].
• Dengue, chikungunya and Zika RT-PCR (return from a Zika transmission area, day 1 to day 7)if neededSuggestive symptoms on return from a Zika transmission area; replaces the dengue-chikungunya PCR (procedures cannot be combined) ^[3].
• Dengue NS1 antigen (day 1 to day 5, if RT-PCR is unavailable)if neededOnly if RT-PCR is unavailable, in a confirmed epidemic and for a simple form; covered from day 1 to day 5 of signs, cannot be combined with the dengue PCR ^[3].
• Dengue IgM and IgG serology (from day 5)if neededFrom day 5: combined with RT-PCR between D5 and D7, alone beyond D7 ^[3].
• Chikungunya IgM and IgG serology (from day 5)if neededFrom day 5: combined with RT-PCR between D5 and D7, alone beyond D7 ^[3].

Depending on the clinical picture

• Stool culture (diarrhoea)if needednon-French guidelineFever with diarrhoea (salmonellosis, shigellosis, Campylobacter: incubation of 2 to 6 days) ^[1].
• Anti-HAV IgM and anti-HEV IgM (jaundice or cytolysis, incubation of 2 to 9 weeks)if needednon-French guidelineHepatitis A (incubation 15 to 50 days) or E (2 to 9 weeks): IgG/IgM serology ^[1].
• Bilharziasis serology (freshwater swimming 4 to 8 weeks before; Katayama fever)if needednon-French guidelineFreshwater exposure: acute schistosomiasis (Katayama fever, incubation of 4 to 8 weeks), diagnosed by serology and by looking for eggs in stool and urine ^[1]. At the onset of symptoms, serology may still be negative: the diagnosis rests on seroconversion, which appears with hypereosinophilia about 3 weeks after the onset of symptoms ^[11].

Before primaquine

• G6PD (if confirmed P. vivax or P. ovale attack)if neededPrimaquine, which eliminates the liver forms of P. vivax and P. ovale, can cause haemolysis in G6PD deficiency. The SPILF (2017) places this test in the initial work-up of these attacks ^[2], as do the United Kingdom, the United States and Germany ^[4,5,13].

At day 3 (72 hours)

• Thin and thick blood film (parasitaemia < 25% of the initial value)

On D7

• Thin and thick blood film (negative parasitaemia)
• FBCif neededAfter treatment with intravenous artesunate (severe attack): delayed haemolysis in 15% of patients, to be looked for on D7, D14, D21 and D28 (haptoglobin < 0.1 g/dL, LDH up by more than 10%, haemoglobin down by more than 10%) ^[2].
• LDHif neededAfter treatment with intravenous artesunate (severe attack): delayed haemolysis in 15% of patients, to be looked for on D7, D14, D21 and D28 (haptoglobin < 0.1 g/dL, LDH up by more than 10%, haemoglobin down by more than 10%) ^[2].
• Haptoglobinif neededAfter treatment with intravenous artesunate (severe attack): delayed haemolysis in 15% of patients, to be looked for on D7, D14, D21 and D28 (haptoglobin < 0.1 g/dL, LDH up by more than 10%, haemoglobin down by more than 10%) ^[2].

At day 14 and day 21 (after intravenous artesunate)

• FBCif neededAfter treatment with intravenous artesunate (severe attack): delayed haemolysis in 15% of patients, to be looked for on D7, D14, D21 and D28 (haptoglobin < 0.1 g/dL, LDH up by more than 10%, haemoglobin down by more than 10%) ^[2].
• LDHif neededAfter treatment with intravenous artesunate (severe attack): delayed haemolysis in 15% of patients, to be looked for on D7, D14, D21 and D28 (haptoglobin < 0.1 g/dL, LDH up by more than 10%, haemoglobin down by more than 10%) ^[2].
• Haptoglobinif neededAfter treatment with intravenous artesunate (severe attack): delayed haemolysis in 15% of patients, to be looked for on D7, D14, D21 and D28 (haptoglobin < 0.1 g/dL, LDH up by more than 10%, haemoglobin down by more than 10%) ^[2].

At day 28

• Thin and thick blood film
• FBCif neededAfter treatment with intravenous artesunate (severe attack): delayed haemolysis in 15% of patients, to be looked for on D7, D14, D21 and D28 (haptoglobin < 0.1 g/dL, LDH up by more than 10%, haemoglobin down by more than 10%) ^[2].
• LDHif neededAfter treatment with intravenous artesunate (severe attack): delayed haemolysis in 15% of patients, to be looked for on D7, D14, D21 and D28 (haptoglobin < 0.1 g/dL, LDH up by more than 10%, haemoglobin down by more than 10%) ^[2].
• Haptoglobinif neededAfter treatment with intravenous artesunate (severe attack): delayed haemolysis in 15% of patients, to be looked for on D7, D14, D21 and D28 (haptoglobin < 0.1 g/dL, LDH up by more than 10%, haemoglobin down by more than 10%) ^[2].