Antenatal prediction of graduated risk of hyaline membrane disease by amniotic fluid foam test for surfactant

FETUS, PLACENTA, AND NEWBORN

Antenatal prediction of graduated risk of hyaline membrane disease by amniotic fluid foam test for surfactant MUREEN

A.

RODERIC

H.

ROB:ERT JOHN

SCHLUETER

K. A.

I’HIBBS CREASY

CLEMENTS*

WILLIAM

H.

San Francisco,

Calij&nia

TOOLEY

We measured amniotic fluid surfactant by the semiquantitative foam stability test within 24 hours before tdelivery of 410 infants, 64 of whom developed HMD diagnosed by standard criteria. When surfactant titers were ranked in eight categories, they predicted graded risks of HMD. On this basis we defilned five “risk groups” with significantly different incidences of HMD (I = 0.5%; II = 10%; Ill = 25%; IV =41%; V = 79%). Infants in Groups I and II were heavier and more mature thanthose in Groups Ill to V. However, among infants of equivalent GA or birth weight, the incidence of HMD still correlated significantly with the foam test results. Within each risk group the incidence of HMD was equal among infants delivered by vagina and by cesarean secfon, slightly greater among males than females, and inversely proportional to GA. In Group V the inddence of HMO was 100% among Infants at less than 33 weeks’ GA. We used this relationship to devise a system that improved predction of HMD by combining the foam test results with GA. (AM. J. OBSTET. GYNECOL. 134:761,

1979.)

GLUCK AND C:O-WORKERS' developedapracticaltest of amniotic fluid for pulmonary sufactant in 1971. Since then, it has become common practice to use such tests as indicators of fetal lung maturity and thereby to From the Cardiovascular Departments of Pediatrics University of California. Supported Pulmonay Received-for Accepted

Research Institute and the and Obstetrics and Gynecology,

by United States Public Health Service SCOR Grants HL-14201 and HL-19185. publication September

May

IO, 1978.

13, 1978.

Reprint reque.yts: Roderic H. Phibbs, Pediatrics, University of CalifoniaSan Francisco California 94143.

M.D.,

*Career

Heart

investigator

0002-9378/79/150761+07$00.70/0~

of the American 1979 The

Department Francisco,

San

Association

C. V.MosbyCo.

of

assess the risk of hyaline membrane disease (HMD) if the fetus were delivered at that time or soon after. A previous preliminary report from this laboratory described a rapid and simple test for pulmonary surfactant in amniotic fluid.* This is commonly known as the “foam test” or the “shake test.” High concentrations of surfactant, “positive tests,” were associated with no HMD and low or nondetectable concentrations, “negative tests,” were associated with a high incidence of HMD. Studies by others have generally confirmed that report and have shown that “false positive” (a positive test for surfactant when the infant subsequently develops HMD) are rare, but that “false negatives” (a negative test when the infant does not develop HMD) are not uncommon. 3, * In this paper we report our more 761

762

Schlueter

et al.

August I, 1979 Am. J. Obstet. Gynecol.

C

0

Positive

F Intermediate Fig.

results

Table

G (* 1

(+ 1

Negative

1. Schematic representation of the foam test and their

I.

Composition

E

I- 1

of eight different possible interpretation (see text).

of tube dilutions

for the

foam test Tube No.

I I Dilution

(cc)

Amniotic fluid Saline (0.9% NaCI) Alcohol (95% ethanol)

I 2 I j

1:l

1 : 1.3

I:2

1.0

0.75 0.25 I.0

0.5 0.5 1.0

1.0

extensive experience with this test and show that the test does not just give an all-or-none prediction of HMD, but a graded estimate of risk for developing HMD. Methods Amniocentesis. Our indications for an amniocentesis to assess fetal lung maturity were: elective termination of pregnancy, including all repeat cesarean sections; indicated termination of pregnancy for such complications as Rh sensitization, severe pre-eclampsia, diabetes mellitus, and fetal distress; and premature labor with advanced cervical dilation. Some patients in the last group had received beta-adrenergic drugs ear-

lier in an attempt to stop labor. Many amniocenteses were performed on preterm pregnancies. In these, the duration of the gestation at time of amniocentesis was determined from the last menstrual period, from the incremental growth of the uterus during gestation, and by the use of ultrasonography in midgestation when appropriate. Amniotic fluid was obtained by transabdominal puncture of the membranes, usually in the suprapubic site, after elevation of the presenting part, or transvaginally by puncture of the bulging membranes. Fluid flowing from a vaginal pool was not used for analysis, nor were samples analyzed if they were meconium stained. A hematocrit was measured on any sample which was blood stained, and if the hematocrit exceeded 3% the fluid was not analyzed. If the hematocrit was between 1 and 3% the fluid was centrifuged for 5 minutes at 500 x g and the test was performed on the supernatant fraction. If the hematocrit was less than 1% the sample was tested without special handling. Foam test. The fluid specimens were tested on the same day they were collected; if not tested within 1 hour, the fluid was refrigerated at 5” C until tested. None of the samples was frozen. The test uses three dilutions of amniotic fluid (these correspond to the first three of the five dilutions previously described*). The amniotic fluid was gently mixed by inverting the tube several times before pipetting the fluid into acidwashed 100 by 14 mm test tubes. The saline* and 95% alcoholt were then added as indicated in Table I. The tubes were capped with rubber stoppers and then shaken by hand by moving the tubes up and down over a 90” arc as fast as possible for 15 seconds. They were then placed in a test tube rack, undisturbed, and after 15 minutes, the air-liquid interface of each tube was examined for the presence of stable bubbles. A tube was recorded as positive (+) when there were enough bubbles present to form a complete ring around the air-liquid interface of the tube (Tube A, Fig. 1). This may be very obvious when the ring of bubbles is several layers deep and covers most of the air-liquid interface (Tube B, Fig. 1). However, the bubbles may be piled up on one side of the tube, or unevenly dispersed around one or more very large bubbles (Tubes C, D, E, Fig. 1). Since the bubbles in tubes C, D, and E would have formed a complete ring if evenly dispersed, tubes with these characteristics were also termed positive. A tube was recorded as intermediate (+) when small bubbles *Distilled make 1,000 tDistilled

water

added

to 9 gm of reagent

grade

NaCl

ml. water,

10 ml, added

to 190 mlof

absolute

ETOH.

to

Volume Number

Amniotic

134 7

fluid foam

test

for surfactant

763

Table II. The eight degrees of reactions from the results of the foam test and incidence of HMD at each reaction

+ +

+ +

+ ”

205 69

+ +

-r _c

‘-

28 18

2 + + -

c k ..-

_’ -

26 22 16 26

0.5

10 11

: 3 4 7 9 13 20

22 27 41

Table III. Risk for developing HMD if delivery within 24 hours of amniotic fluid foam test

is

2:: I II

III IV V

+

+

+

t t

+

?

t

-t

+-

:t

2

:C_ :‘I

2 -

-rr -

-

-

__

Table IV. Birth risk group

I II III IV V

weight

205

97 44 22 42

l/205


IO/97

10

1 l/44

25

9122

41

33142

79

and GA for each

3,275 2,774 2,333 2,475 2,124

+” f _’ 2

703 856 999 994 1,000

39.2 36.8 34.5 35.0 33.5

2 2 k t k

2.5 3.2 3.8 3.3 3.2

were present but not in sufficient numbers to form a complete ring iaround the tube (Tubes F and G, Fig. 1). A tube was negative (-) when there were no bubbles present (Tube H, Fig. 1). Fig. 2 shows photographs of four foam test reactions and their interpretations. Patients. In all cases included in the analysis the infants were born within 24 hours of a successful amniocentesis and. completed foam test. Twins were included only when we could identify the twin from whose amniotic sac we obtained the fluid for analysis. Asphyxiated infants were all resuscitated in a standard fashion previously described.5

Fig. 2. Actual photographs pretation.

of the foam test and their inter-

HMD was diagnosed when an infant showed all of the following: miliary atelectasis on chest x-ray; inspiratory retractions of the chest wall and expiratory grunting; venous admixture in arterial blood; and a course in which these signs lasted at least 72 hours and progressively worsened for at least the first 48 hours, or until institution of assisted ventilation. Infants with transient tachypnea of the newborn, transient respiratory distress following intrapartum asphyxia, aspiration of meconium-stained amniotic fluid, or bacteriologic or postmortem findings of pneumonia were considered to have no HMD.

Table V. I‘he survival of infants lvith HX11) risk group and type of respiratory therapy

in exh

7‘rralnlrtrl

H,MD

Kiqk group

lhrrl

0,

Auisfd

urtzlilatiot~

Results 01‘ the -110 infants born within 24 hours after an amniotic. fluid specimen was obtained, 232 were at less than 39 weeks’ gestation. In 20.5 of the 410 the foam test reaction was positive in all three dilutions and only me of. these infants developed HMD. J n the other 3% the reaction was intermediate or negative in one OImart: of’ dir\ three dilutions, and 64 of these infants developed HMD. Since the test has three possible reactioris in each of three dilutions t,he results can be ranked in order of eight degrees of reaction as a titer of amniotic. fluid surf‘actant. WC did this and compared the incidence of H&ID between the reaction groups (shown in Table II).* There is a progressive increase in incidence of’ HMD with decreasing reaction. The data fail into five groups as shown in Table III. The difference in incidence of HMD between groups is significant by a 2 x 5 chi-square analysis (p < 0.001). All subsequent analyses are based on the five risk groups defined in Table III. Tahlc IV shows the birth weights and gestational ages ((;A) f’or each group. The infants in the lower risk groups with more detectable surfactant tended to br larger and more mature. The differences between the gi-oups were compared by means 01 the Newman-Keuls nit1ltiple range test t’or significance at the 0.05 level.” ‘1‘1~ infants in Group I I\-err significantly heavier and ~norc’ mature than those in each of. the other groups. ‘l’lic i11fants in Groi1l~ II were significantly hcaviei- and 111o1.cmature t ha11 the inpants in Groups I I J and LT. ‘I‘here were no other significant clif.ftrences betwec11

LVithi11 eat11 amniotic Ruitl 1-1sk group the risk 01 HLID was rclatetl to botl1 IGrth weight antI t;.\. Tllose wt10 dc\.i,q,ed JHMD were signific,1ntlv sm;illcl and less mature. as shown in I’ablc \‘I. ‘The i11citititce of HMD was not signif1cantiy greato ;11no11g~~cu~‘ea~~ section-delivered int’zuits than an1ctng vaginall\ drlivered infants xvitt1in any gro11p ant1 there \vas no over-all tendencv toward 11101-c FihfI) aftel~ cx3;11x2n stzction dclivery. ‘l‘herr \\a~. however. a tenticiic! foi 11101.~nidles than female\ within eacl1 risk group to ha\c HMD. This was not statisticali\ significant !2-ithi1i an\ Gngle yfl-ollp,

ht

the

Owls-all

twnd

all

;rtllorlg

toll1

g1wups

chi-scliiarc aiiai\ci5 (p < O.OI,l. Table C;Il show\ a more dctailcd analvsis oi f(,;un test reactio11. (;.A. at1d rish of’ HMII. \t a givvt1 Ic\el 01 reaction, risk of HMD drc~~ascs ah gestatio11 it1Crt’a\t‘s. On the othv1 hi111tl. at ;I give11 gcstatio11,1l ‘1s~. risk ot HMD decreases as suri’actant titer i11c1-cascs. Note that there art’ no “ki1lSe iregati\e” It’41 ‘lltlollg ttti. le5;s Illilture infants. t\ll infants bor11 bclort* 33 \\,evk\’ gestation in Group \’ tle~elol~d HXiI). was

sigliiticcilil

tx

Comment I‘hcsr

“111 addition to the eight reactions shown in Table 11, there at‘r others which occur only rarely. There can be a twofold change between dilutions (+ + - or + - -). We saw this reacrion in only three cases; none of the infants had HRID. Since these reactions did not fit logically into the sequence shown iu Table II, and we had no extra amniotic fluid to repeat the test. we omitted them from the analysis. There can also be a r‘eversal of the degree of reaction with dilution (+?+ or -t-k). ‘This is most easily explained by pipetting error and when this occurred we always had extra fluid to repeat the test. On retesting, the result was always one of the common r-eactions, i.c,.. +k+

became

+++

and’&-?

became

tti.

&la

ct1orv

tht

ttw

loall~

te\t

CalI

ix

used

IO

accurate+ predict a graded risk of an inf’zmr developing HMD if delivered within 24 houn s after tl1e test. .I‘hia is more useful than a test \\-hicti siinply indicates \vlreii the lungs have fl~ll) matured and the risk of HND toilo~ving deliver! is extremely ION. Iii many high-i,isk ptqnancies tbc risks of continued intrauterine tit’e 111ust be weighed against the risks of’ premature delivery. In these Gtuations. tt1c ability to predict tcvels of 1-isk tot HMI) can be verv useful. For csamplc, i1r \omc’ high-

Volume Number

Amniotic fluid foam test for surfactant

134 7

Table VI. Birth weight, each risk grmoup Rtik

II

gray?

GA, sex, and type of delivery

NO.

for infants

Birth wright (gm) (mean t S.D.)

w+th and without

GA (wk) (mmn f S.D.)

HMD

within

SfX ,M IF

HMD No HMD

10

2,231 t 781

87

2,836

? 846

34.7 37.1

F 3.6 2 3.1

HMN No HMD

11 33

1,412 2,640

t 339 r 928

30.3 36.0

k 2.8 r 3.0

9 13

2,113 2,724

1 1,150 -t- 826

32.9 36.4

‘- 3.3 2 2.5

33

9

1,994 2,603

-c 933 -+ 655

32.8 36.4

-t 3.0 k 1.Y

associations

of foam test and GA with the risk of HMD

765

D&very

vag. lce.rarean

4- 73 46 41

-I- 87 40 47

III

IV HMD NoHMD V HMD No HMD

Table

VII.

Independent

GA (wk)

Risk group

5.29 HMDltotal

m-32 HMDltotal

33-35 HIMDltotal

I

O/l

Oil

Oil2

II

o/2

3111 (27%)

3114 (21%)

616 (100%)

318 (38%)

(8%)

IV

212 (100%)

213 (67%)

V

616 (100%)

lo/lo (100%)

III

risk pregnancies one might choose to allow the pregnancy to continue rather than deliver an infant with a 40% or 80% risk of HMD. Once the risk of HMD falls to 10% or even 25%, delivery might be safer for the mother or fetur; than continuing the pregnancy. Studies in animals indicate that pulmonary surfactant first appears in fetal tracheal fluid and amniotic fluid in low concentrations. Then, late in gestation, the concentration increases rapidly to the level present at the end of pregnancy. 3, 1 Studies of human amniotic fluid have shown that the concentration of surfaceactive phospholipid and of an apoprotein unique to pulmonary surfactant rise in a similar fashion during gestation and that the risk of HMD is inversely proportional to the surfactant concentrations present at birth.‘, 3, 4. x There is a surfactant level above which HMD is relatively rare. Below that level, it becomes more common and the incidence tends to increase progressively as surfactant concentration decreases.“, “’ The eight levels of foam test reaction appear to span

1112

36-38 HMD /total

39-41 HMDltotal

z-/2 HMDltotal

1155 (2%)

01102

0134

3140

1127 (4%)

013

(8%) l/l0 (10%)

018

215 (40%)

319 (33%)

013

719 (78%)

10116 (62%)

Oil

most of the range of concentration from the immature to the fully matured lung, thus giving a semiquantitative measure of surfactant concentration. We related amniotic fluid surfactant only to HMD, not to other forms of neonatal respiratory distress, since this is the only disease which has been linked by pathophysiologic studies to delivery before the pulmonary surfactant system has matured sufficiently to produce lung stability.” Many authors have suggested that acute intrapartum insults, particularly asphyxia, may play a secondary role in the development of HMD by interfering with the function of the surfactant system and increasing the risk of HMD, particularly in an infant in whom the surfactant system is only partially matured.“, ‘. R. ‘l-l’ If this thesis is correct, early and vigorous resuscitation may ameliorate some cases of HMD. In that case, the potential incidence of HMD may be somewhat greater than is shown in our risk groups, since all asphyxiated infants in this study received prompt and vigorous resuscitation.

766

Schlueter

et al.

HMD RISK (%)

+--

tt_.

+++ FOAM

TEST

++-

+++

+++

a++

REACTION

Fig. 3. Scheme for antenatal prediction of HMD l’rom amniotic fluid foam test reaction plus GA. Foam test reaction is OII the longitudinal axis and risk of HMD on the vertical. ‘The risk is predicted horn the shaded band appropriate for GA. ‘I‘he width of’ each hand approximates the error of the estimate. For example, with a toam test reaction ot ft? the risk ot HMD is approximately 1.5% it the GA is >33 weeks, 55% if the GA is 3 1 to 33 weeks, and appl-oximately 90% if it is
Low birth \\ei$~t ant1 5lrc)t.t (iA ;~tc~associ;ttcd ~itlt ;f high incid~~l1c~c of HhlD.“~ ’ Our d;rt;r ~11-orlgI~ \LIgpcst that there is mo~c than one c ompott~nt to this ;ISSOCiation. hmniotit fluid surfacl;tnl ~oi1~~t’i1ti~;itioii ptcdic,ts the risk ot’ fH’\ID indcpcndcnt q)f \\Ggilt ot gtbstation. Since infants wtth Iowct- 5rirf’;tc.f,int ~ot1~~f~1ttt~;itiot1sarta smaller ;rn(l le\s r11atttrc 011 the ;tvtst-age, pa1.i (,I ttr< associatiot1 ot weigh1 and gestatiott \\ttli fIbI risk is through surf,t( tant maturation. tIo\\r~c~:, ,II ‘1 given test level, tl~(. risk 01’ HMD decrcast~ c\ith it1crcasing gestation 01‘ \\eight and. ther~fo~-C. ;tppar~ntl~ in& pcndently of lung maturation. l’ablc \‘I1 ~11~;~~5 the interactiott l\ith GA. ‘I’l~ur. an1011,q infattts at :$‘L \vecks’ gestation 01’ Ircr. the inc-idctict~ of t-1511) is 1009; if’ the toam test i5 crjmplrtely ncg-ati\,c. ‘I hi5 i\ cott\iiitc‘ttt with the findings of ~veral other invcstigato1\ uxittg the foam teht 01 tltc Lit, intio 011 ,Intiiititic Illlid ot the roam tcsf 011 qstric ;~lI) lllilll curJ;tct;ttit titer alone still do. T‘hc ~hcme for antcnat.;il prctliction of HhlD i$ ~ho~11 in I+i,q. :i. -1%~ method of the test is simple, but it is important to adhere strictly to thr (letilils of the rrle111od. Intcrprcration of thr. reaction in v2r.h tulw d\ i. * 01. - i\ usually clear- 2nd eas! if one fi)llows the (‘rlterl;i we havt explained ;iiitl illustrated above. ~IORYIYI., cvc yttggest that the rcliattilit! of tht, tc\t \\ill bc bclttcr if it is ~EI formed 11) ;I tt~ctitiiciati pt.opct 1) trainc~rl in tltt. nrt~thotl arid a~~t1st~~t11c~Ito rc~;ttliriCg ttie rcactioiis itI IIt<, 1111~s. This is th(L \\;I\ \vc ha\? pei tormetl the 1(‘s! ,ttitl wc doubt that it \cottld he quallv 1 eliahlv it pc~rlormed 1,~ incxperienc-ed persortc. The clinical staff of the Perinatology Sct\,~cs, tf. (:. Moffitt Hospital, and tl1c tcclmical s1ai.t. of tlte Clinical Physiological Services, <;arctio\,asc-ttl~~r Research Institute,

pi-ovidcd

stttdie\.

i~Vi~ltl;tlAr

;tssis;tanc.c

I0

Its \\itll

tllfzse

Volume Number

Amniotic fluid foam test for surfactant

134 7

REFERENCES 1. Gluck, L., Kilovich,

9. Donald,

M. V., Borer, R. C., Brenner, P. H., Anderson. G. G., and Spellacy, W. N.: Diagnosis of respit-atory distress syndrome by amniocentesis, AM. J. OB-

STET. GYNECoL.

1@k+io,

1971.

2. Clements, ,J. A., Platzker, A. C. G., Tierney, D. F., Hobel, C. J., Greasy. R. K., Margolis, A. J.. Thibeault, D. W., Tooley, W. H., and Oh, W.: Assessment of the risk of respiratory distress syndrome by a rapid test for surfactant in amniotic fluid, N. Engl. J. Med. 286:1077, 1972. 3. Farrell, P. M., and Avery, M. E.: Hyaline membrane disease, Am. Rev. Resp. Dis. 111:675, 1975. 4. Farrell, P. M.: The prevention of hyaline membrane disease: New concepts and approaches to therapy, Adv. Pediatr. 23:213, 1976. 5. Phibbs, R. H., Johnson, P., Kitterman, 1. A., Gregory, G. A., and Tooley, W. H.: Cardiorespiratory states of ervthroblas:otic infants. Pediatrics 48:5. 1972. 6. Zar, J. H.: Biostatistical Analysis, Englewood Cliffs, N. J., 1974, Prentice-Hall, Inc. 7. Gregory, G. A., Kitterman, J. A., Phibbs, R. H., Tooley. W. H.. and Hamilton. W. K.: Continuous oositive airwav pressure as treatment in the idiopathic respiratory distress syndrome, in Stetson, J. D., and Swyer, P. R., editors: Neonatal Intensive Care, St. Louis, 1976, Green, pp. 309-326. 8. King, R. J., ;Ruch, J., Gikas, E. G., Platzker, A. C. G., and Creasy, R. K.: Appearance of apoprotein of pulmonary surfactant in human amniotic ‘fluid, J. Appl. Physioj. 39:735, 1975.

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767

1. R., Freeman, R. K., Goebelsmann, U.. Ghan, W. H., and Nakamura, R. M.: Clinical experience with the amniotic fluid lecithinispingomyelin ratio, AM. J. OBSTET.GYNECOL. 115:547, 1973. Keniston, R. C., Pernoll, M. L., Buist, N. R. M., Lyon, M., and Swanson, J. R.: A prospective evaluation of the lecithinisphingomyelin ratio and the rapid surfactant test in relation to fetal pulmonary maturity, AM. J. OBSTET. GYNECOL. 121:324, 1975. Cruz, A. C., Buhi, W. C., Birk, S. A., and Spellacy, W. N.: Respiratory distress syndrome with mature lecithin/ sphingomyelin ratios: Diabetes meltitus and low Apgar scores, AM. J. OBSTET. GYNECOL. 126:78, 1976. Thibeault, D. W., and Hobel, C. J.: The interrelationship of the foam stability test, immaturity and intrapartum complications in the respiratory distress syndrome, AM. J. OBSTET.GYNECOL. 118~56, 1974. Gluck, L., Kulovic, M. V., Borer, R. C., and Keidel, W. N.: The interpretation and significance of the lecithin/ sphingomyelin ratio in amniotic fluid, Abr. J. OBSTET. GYNECOL. 120:142, 1974. Chu, J., Clements, J. A., Cotton, E. K., Klaus, M. H., Sweet, A. Y., and Tooley, W. H.: Neonatal pulmonary ischemia, Pediatrics 4O(Suppl):709, 1967. Evans, J. J.: Prediction of respiratory distress syndrome by shake test on newborn gastric aspirate, Iv. Engl. J. Med. 292: 1113, 1975.